Tag: Conversions

You're on a road trip, the speed limit shows 65 mph and you want to know if you're about to get a ticket. A European friend tells you they weigh "80 kilos." The recipe calls for 200 °C and your oven only speaks Fahrenheit. You don't always have a calculator at hand — and for daily life, you don't need one.

With these mental approximations you'll be accurate enough in everyday situations, and you'll know exactly when you need real precision (spoiler: in science, medicine and money, there are no shortcuts).

The 5 shortcuts that pay off most

1. km → miles: divide by 8 and multiply by 5. 80 km → 50 miles (exact: 49.7).

2. °C → °F: double and add 30. 20 °C → 70 °F (exact: 68). Perfect for weather.

3. kg → pounds: double and add 10 %. 5 kg → 10 + 1 = 11 lb (exact: 11.02).

4. m → feet: multiply by 3 and add 10 %. 2 m → 6 + 0.6 = 6.6 ft (exact: 6.56).

5. liters → gallons: divide by 4. 8 L → 2 gal (exact: 2.11).

Mental anchor table

These anchors are your safety net: any conversion that strays far from them is probably wrong.

More useful shortcuts for daily life

• km/h → mph: divide by 8 and multiply by 5 (same as km → miles). 100 km/h → 62 mph (exact: 62.1).
• cups → ml: multiply by 240. 1.5 cups → 360 ml.
• °F → °C: subtract 30 and divide by 2. 70 °F → 20 °C (exact: 21.1).
• hectares → m²: multiply by 10,000. Handy when reading land listings.
• ounces → grams: multiply by 28 and add 2 %. 4 oz → 114 g (exact: 113.4).
• feet → cm: multiply by 30. 6 feet → 180 cm (exact: 182.9).

When NOT to use tricks

• Delicate baking: use exact grams; a 5 % error ruins a meringue.
• Fuel or aviation: knots, Mach and fuel liters require precision.
• Data storage: KB vs KiB leaves no room for approximations (a "1 TB" drive is really 931 GiB).
• Any payment, legal measurement or dose: here "good enough" isn't good enough.

How to practice in 5 minutes a day

Pick a personal anchor: your height, the weight of your suitcase, the distance of your running route. Every time you see a number in a different unit (a speed limit in mph, a recipe in cups, a weight in pounds), convert it mentally and check it with the calculator. Within two weeks, the most common conversions become automatic — and within a month, you'll do them without thinking.

FAQ about mental conversion

What is the most useful mental trick?

km → miles (÷8 ×5) and °C → °F (×2 +30) cover 80 % of everyday conversions.

Do these tricks work for exams?

For approximating yes; for exact answers, use the full formula. A teacher won't accept "roughly."

How do I improve my mental conversion?

Practice with known anchors: your height, the weight of a bag, your road speed.

How much error do these tricks have?

Between 1 % and 5 % depending on the shortcut: good enough for daily life, not for science, medicine or money.

Need total precision? Use the unit calculator and forget the tricks — exact, fast and without rounding errors.

A boat "does 20 knots," a plane flies at "Mach 0.85" and your car shows 120 km/h. Three environments, three different units. And if you rent a car in Europe, the speedometer is in km/h even though you think in mph.

Speed is measured differently depending on the medium: km/h on the road, knots at sea and in the air, Mach in high-performance aviation, m/s in science. Converting between systems isn't hard once you know the factors — and it can prevent serious misunderstandings (like mistaking a 50 mph limit for 50 km/h).

The base speed units

• km/h: kilometers per hour, the usual road unit (Europe and most of the world).
• m/s: meters per second, the International System unit.
• mph: miles per hour, used in English-speaking countries.
• Knot (kn): 1 nautical mile per hour = 1.852 km/h.
• Mach: speed relative to the speed of sound (≈ 1225 km/h at sea level).

Quick speed conversion table

Practical speed conversion examples

• Road: 100 km/h in m/s → 100 ÷ 3.6 ≈ 27.8 m/s.
• Sea: a boat at 20 knots → 20 × 1.852 ≈ 37 km/h. A knot is almost double a km/h.
• Air: a commercial jet at Mach 0.85 → 0.85 × 1225 ≈ 1041 km/h.
• Europe: a 65 mph limit → 65 × 1.609 ≈ 104.6 km/h. It's not "65 km/h."

Reference speeds to get your bearings

These anchors let you check at a glance whether a conversion is reasonable: if a car is "doing 300 knots," something is off (that would be 555 km/h — five times an F1 car).

Speed in sports and running

Athletics uses pace in minutes per kilometer, not speed. A 5 min/km pace equals 12 km/h (60 ÷ 5). To go from pace to speed: speed = 60 ÷ pace. And in swimming or sailing, distances are given in nautical miles, so times are computed in knots.

Common speed conversion mistakes

• Confusing knots with km/h: a knot is almost double (1.852).
• Treating Mach as a fixed factor: it depends on altitude and temperature; at 10,000 m sound travels slower than at sea level.
• Reading foreign speedometers as if they were local: 100 mph is not 100 km/h — it's 161 km/h.
• Forgetting the 3.6 when converting m/s to km/h.

FAQ about speed conversion

How many km/h is one knot?

Exactly 1.852 km/h (one nautical mile per hour).

What is Mach 1?

The speed of sound: about 1225 km/h at sea level. It decreases with altitude and temperature.

How do I convert km/h to m/s?

Divide by 3.6. The other way, multiply by 3.6.

What speed is a 5 min/km pace?

60 ÷ 5 = 12 km/h.

How much is 100 mph in km/h?

100 × 1.609344 ≈ 161 km/h.

Convert speeds between km/h, knots, mph, m/s and Mach with the unit calculator — instantly and without errors.

You found the perfect cake recipe on a European blog: "500 ml of milk, 200 g of flour." Your kitchen measures in cups and spoons. Do you start improvising or do you know how to convert?

European recipes use grams and milliliters; Anglo-Saxon ones use cups, tablespoons (tbsp) and teaspoons (tsp). Converting volume correctly is the difference between a fluffy cake and a brick. And there's a detail almost nobody knows: a cup is not the same everywhere.

Cooking volume units

• 1 cup = 240 ml in the US (250 ml in the UK)
• 1 tablespoon (tbsp) = 15 ml
• 1 teaspoon (tsp) = 5 ml
• 1 fluid ounce (fl oz) = 29.57 ml
• 1 pint = 473 ml in the US (568 ml in the UK)

Quick volume conversion table

Practical cooking conversion examples

• 2 cups of flour: 2 × 240 = 480 ml (but in weight that's ~240 g of flour, not 480 g: volume is not weight).
• Half a teaspoon of salt: 2.5 ml.
• 1 liter of milk in cups: 1000 ÷ 240 ≈ 4.17 cups, i.e. 4 cups plus a tablespoon.
• Cocktails: 1.5 oz of spirit → 1.5 × 29.57 ≈ 44 ml, the standard drink measure.

Common volume conversion mistakes

• Using the US cup (240 ml) in British recipes (250 ml): the difference is small but real in baking.
• Confusing the weight ounce (28.35 g) with the fluid ounce (29.57 ml): completely different units.
• Measuring dry and liquid ingredients with the same cup without leveling: flour should be leveled, not packed.
• Assuming 1 cup weighs 240 g: it depends on the ingredient (see the density table below).

Scaling recipes without breaking them

If a recipe for 4 people uses 2 cups of broth and you want it for 6, multiply everything by 1.5: 3 cups. But salt and spices don't always scale linearly: add them at the end and taste. To convert a recipe from cups to grams, use each ingredient's density:

At the bar and in cocktails

Cocktail recipes use fluid ounces and "dashes." A standard liquor measure is 1.5 oz ≈ 45 ml, and a shot is 1 oz ≈ 30 ml. Converting your jigger to ml avoids surprises with both the alcohol content and the flavor balance.

FAQ about volume and cooking measurements

How many ml are in a cup?

240 ml in the US; 250 ml in the UK and many European recipes.

How many tablespoons are in a cup?

16 tablespoons (15 ml each).

Are weight and volume interchangeable in cooking?

No: 1 cup of flour weighs ~120 g and 1 cup of sugar ~200 g. Use volume for liquids and weight for dry ingredients when you can.

How many ml are in 1.5 fluid ounces?

1.5 × 29.57 ≈ 44 ml, the standard cocktail measure.

How many liters are in 8 cups?

8 × 240 = 1920 ml ≈ 1.92 liters (almost 2 — the classic "drink 8 glasses of water a day").

Convert cups, liters and ml instantly with the unit calculator and cook without drama.

Your timesheet says you worked 7.5 hours and your payroll shows 7 hours 30 minutes. A movie runs 2 h 15 min and you need the seconds for a calculation. And when booking an international flight, is 3 PM 15:00 or 03:00?

Time uses the sexagesimal system (base 60), not decimal. That's why 1.5 hours are not 1 hour 50 minutes, but 1 hour 30 minutes. Mastering these conversions saves you mistakes at work, when traveling and in daily life.

The base rules of time

• 1 minute = 60 seconds
• 1 hour = 60 minutes = 3600 seconds
• 1 day = 24 hours = 1440 minutes
• 1 week = 7 days

Quick time conversion table

Practical time conversion examples

• 2.5 hours in minutes: 2.5 × 60 = 150 min.
• 90 minutes in hours: 90 ÷ 60 = 1.5 h.
• A 2 h 15 min movie in seconds: 2 × 3600 + 15 × 60 = 8100 s.
• A week in hours: 7 × 24 = 168 h.

Decimal hours at work: the most common case

Many companies log working time in decimal format (7.5 h), but payroll and timesheets are read in hours and minutes. To turn 7.5 hours into hours and minutes: 0.5 × 60 = 30 → 7 h 30 min. And the other way: 8 h 45 min is 8 + 45/60 = 8.75 h.

12-hour and 24-hour formats

To go from 12-hour time to 24-hour time: afternoon hours add 12 (3 PM = 15:00); early morning hours subtract 12 (3 AM = 03:00). Noon is 12:00 and midnight is 00:00. This mistake is typical when booking flights or international meetings: a "3:00 PM" flight departs at 15:00, not 3 in the morning.

Common time conversion mistakes

• Treating hours as decimals: 1.5 h is 90 min, not 1 h 50 min.
• Forgetting that a day has 24 hours when calculating deadlines (a "3-day deadline" is 72 hours, not 36).
• Confusing AM/PM when converting between clock formats.
• Adding minutes directly: 1 h 45 min + 45 min = 2 h 30 min, not 1 h 90 min (and 90 min becomes 1 h 30 min).

FAQ about time conversion

How many seconds are in an hour?

3600 seconds.

How many hours are in a week?

168 hours (7 × 24).

How do I convert 0.25 hours to minutes?

0.25 × 60 = 15 minutes.

How do I convert 2.75 hours to hours and minutes?

0.75 × 60 = 45, so it's 2 h 45 min.

What time is 3 PM in 24-hour format?

15:00.

Convert hours, minutes and seconds without thinking with the unit calculator — sexagesimal time solved in seconds.

You're buying a 55-inch TV and need to know if it fits the cabinet. Your friend from Europe says they're 180 cm tall and you have no idea how many feet that is. Or you're following a DIY tutorial that asks for "2 feet of cable."

Converting length units is one of the most practical skills you can have: you travel, shop online, exercise or study, and the metric system (mm, cm, m, km) constantly collides with the imperial one (inches, feet, yards, miles). The good news: with a few rules and factors, you'll never hesitate again.

The golden rule: everything comes down to the meter

The meter is the base unit of the International System (SI). All metric prefixes only change the scale, so converting within the metric system is just moving the decimal point:

• 1 km = 1000 m
• 1 m = 100 cm = 1000 mm
• 1 cm = 10 mm

Memorize this ladder and any internal metric conversion (km → m → cm → mm) is instant. The real challenge is jumping to imperial units — and that's what the factors below are for.

Quick length conversion table

Bookmark this table or, better yet, use the unit calculator and forget about memorizing.

Practical length conversion examples

• Height: 5 feet → 5 × 0.3048 = 1.524 m. With inches too (5'11"), first convert the feet: 5 × 12 = 60, add 11 → 71 inches, then × 2.54 → 180.3 cm.
• Screens: a 55-inch diagonal → 55 × 2.54 = 139.7 cm. Screens are always measured in inches, even in metric countries.
• Distance: 10 km in miles → 10 ÷ 1.609344 ≈ 6.21 miles. Note: you divide, not multiply.
• Bike wheels: 26" and 29" are inch diameters → 66 cm and 73.7 cm.

Length conversions you meet every day

• Clothing sizes: size charts mix cm and inches depending on the brand; waist sizes usually come in both.
• Sports: races use km; American football uses yards (a field is 100 yards = 91.4 m).
• DIY and plumbing: pipes and tools in inches (1/2", 3/4") even where everything else is metric.
• Aviation and sailing: distances in nautical miles (1 nm = 1.852 km), which is why the nautical mile is in the table.

Common length conversion mistakes

• Confusing inches with centimeters: a 55" screen is not 55 cm — it's 139.7 cm.
• Forgetting that 1 foot = 12 inches, not 10: imperial is not decimal.
• Using the factor backwards: km to miles divides; miles to km multiplies. Always sanity-check the result (a mile ≈ 1.6 km).

FAQ about length conversion

How many centimeters are in an inch?

Exactly 2.54 cm.

How many feet are in a meter?

About 3.2808 feet (3 feet and 3.37 inches).

Land mile or nautical mile?

The statute mile is 1.609344 km; the nautical mile is 1.852 km (one minute of latitude).

How long is a yard in meters?

0.9144 m, almost a meter — which is why yards and meters get confused so often.

How do I convert 5'11" to centimeters?

(5 × 12 + 11) × 2.54 = 180.3 cm.

Need to convert any length unit instantly? Try the unit calculator and get the exact result in seconds — no tables, no formulas.

In 1983, an Air Canada flight ran out of fuel mid-flight because one crew calculated in pounds and another in kilograms. In 1999, the Mars Climate Orbiter disintegrated because one team used newtons and another used pound-force. And in your kitchen, a cake turns into a brick because you used a 240 ml cup instead of a 250 ml one.

Most conversion errors aren't about math — they're about method. These are the most repeated failures and how to dodge them for good.

The 10 most common conversion mistakes

1. Backwards factor: converting km to miles by multiplying by 1.609 instead of dividing. Always check whether the result makes sense.

2. Misplaced decimals: 1 km is 1000 m, not 100 m. Count the zeros.

3. Mixing systems: using 2.54 (inches → cm) when you're working with feet.

4. Confusing weight and volume: 1 cup doesn't weigh 240 g for every ingredient (flour weighs ~120 g).

5. Forgetting to subtract 32 in Fahrenheit → Celsius.

6. Using the wrong cup: 240 ml (US) vs 250 ml (UK).

7. Rounding too early: 454 g is not 500 g in a delicate recipe.

8. Confusing decimal KB with binary KiB when calculating storage (a 500 GB drive shows 465 GB).

9. Treating time as decimal: 1.5 h is 90 min, not 1 h 50 min.

10. Not verifying with a known case: 1 m ≈ 3.28 ft is a mental anchor that saves you.

Quick verification tricks

• Mental anchors: 1 inch = 2.54 cm, 1 kg ≈ 2.2 lb, 1 mile ≈ 1.6 km, 1 cup ≈ 240 ml.
• Sanity check: 30 cm is roughly a foot, 1 liter is almost a quart, 20 °C is ~68 °F.
• Order of magnitude: if you convert 5 km and get 0.003 miles, something is wrong. A result should "look" right.

The inverse conversion as a check

The fastest way to validate a conversion is to do it backwards. If you converted km to miles and got 6.2 miles, convert 6.2 miles back to km by multiplying by 1.609: you should recover your 10 km. If it doesn't close, the error is in the factor or in the operation (multiplying instead of dividing). This trick works with any unit and takes five seconds.

Context-specific mistakes

• Recipes: confusing oven temperature (°C vs °F) or cups from different countries.
• Tech: mixing decimal KB with binary KiB when buying storage or calculating downloads (300 Mb/s ≠ 300 MB/s).
• Travel: assuming speed limits in mph are km/h (65 mph is 105 km/h).
• Sports: reading pace (min/km) as speed (km/h): 5 min/km is 12 km/h.
• Finance: rounding exchange rates or percentages too early.

FAQ about conversion mistakes

What is the most common conversion mistake?

Using the conversion factor backwards. Always check whether the result makes sense.

How do I know my conversion is correct?

Compare it with a known anchor value (1 kg ≈ 2.2 lb) or run the inverse operation.

Is it worth memorizing factors?

Only a few anchors; for the rest, use a conversion calculator. Memorizing 20 factors is a waste of time.

Should I round the result?

Round only at the end and according to use: cooking and DIY tolerate rounding; money, science and medicine do not.

Avoid these mistakes and convert accurately with the unit calculator — the exact result, every time.

Your favorite European baking recipe calls for "500 g of flour" and your measuring cups are in cups. At the gym, the dumbbells are marked in pounds but your tracking app wants kilograms. And when you ship a parcel abroad, the carrier quotes in pounds and ounces.

Grams, kilos, pounds and ounces coexist in the kitchen, the gym, shipping and food labels. Converting between them isn't advanced math: it's knowing four factors and a couple of tricks. Let's get to it.

The base: the kilogram

The kilogram is the base unit of mass in the International System. Everything else follows:

• 1 kg = 1000 g
• 1 g = 1000 mg
• 1 metric tonne = 1000 kg

Fun fact: since 2019 the kilogram is no longer defined by a physical object (the famous "master kilo" in Paris) but by the Planck constant. For everyday conversions, nothing changes: the factors stay the same.

Quick weight conversion table

Practical weight conversion examples

• Gym: a 20 kg barbell → 20 × 2.20462 ≈ 44.1 lb. Those American 45 lb plates are actually 20.4 kg.
• Cooking: a pound of meat → 0.453592 kg ≈ 454 g. An ounce of cheese → 28.35 g.
• Shipping: a 5 kg package → 5 × 2.20462 ≈ 11.02 lb. If the rate is per pound, every 0.45 kg counts as one more pound.

Weight in the kitchen: scales don't lie

Anglo-Saxon recipes give dry ingredients in cups and liquids in fluid ounces, but weight is always more reliable: 1 cup of flour weighs about 120 g and 1 cup of sugar about 200 g. If a recipe says "1 lb of butter", that's 454 g (usually 2 cups or 4 sticks). When converting recipes, weigh whenever you can: scales don't fail, cups do.

Weight in shipping and international parcels

Couriers quote in pounds and ounces (US) or kilos (Europe). And watch out for volumetric weight: carriers compare the real weight with the volume (length × width × height ÷ factor) and charge the larger one. A big, light box can cost more than a small, heavy one even though it weighs less.

Common weight conversion mistakes

• Forgetting that 1 lb = 16 oz: it's not decimal.
• Rounding too early: 454 g is not 500 g in a delicate recipe.
• Confusing tonnes: the metric tonne (1000 kg) and the US short ton (907 kg) are different units.
• Mixing weight ounces (28.35 g) with fluid ounces (29.57 ml): completely different units.

FAQ about weight and mass conversion

How many pounds are in 1 kilo?

2.20462 pounds. Mental trick: double and add 10 % (1 kg → 2 + 0.2 = 2.2 lb).

How many grams are in an ounce?

28.3495 grams — call it 28 g and you're close enough for most cooking.

Are weight and mass the same?

Technically no: weight depends on gravity, mass doesn't. But everyday conversions use the same factors.

How many ounces are in a pound?

Exactly 16 ounces.

How much does a cup of flour weigh?

About 120 g; a cup of sugar about 200 g. Weight per volume changes with every ingredient.

Convert kilos, pounds and ounces instantly with the unit calculator — no mental tables, no rounding errors.

Before the metric system, every region used its own measurements: a "pound" could weigh differently in two neighboring towns, and a "foot" wasn't the same foot in Paris as in London. For trade, it was absolute chaos.

Today, 195 countries agree on meters and kilos. How did we go from a jumble of local measures to a universal system? The answer starts with the French Revolution and ends with the speed of light and a quantum physics constant.

The origin: France, 1791

In the middle of the French Revolution, the National Assembly commissioned a system of measurements based on nature, not on a king or any single city. That's how the meter was born: initially defined as one ten-millionth of the quadrant of the Earth's meridian. The idea was that anyone, anywhere, could reconstruct the measurements without depending on an arbitrary standard.

Key milestones of the metric system

• 1795: France officially adopts the metric decimal system.
• 1875: the Metre Convention creates the International Bureau of Weights and Measures (BIPM) and the famous "master kilo" in Paris.
• 1960: the International System of Units (SI) unifies and modernizes the system.
• 1983: the meter is redefined using the speed of light, leaving the meridian behind.
• 2019: the kilogram is redefined using the Planck constant; the "master kilo" in Paris retires after 130 years of service.

Who uses what today?

Almost everyone uses SI. The most visible exceptions: the United States (imperial in daily life), Liberia and Myanmar. The UK is a curious mixed case: kilometers on the road, but pints and pounds at the pub.

Why it matters: the price of unit errors

A single system avoids expensive errors. The most famous case: the Mars Climate Orbiter (1999) was lost — about $125 million — because one team used newtons and another used pound-force. In daily life, a common system makes recipes, clothing sizes, tools and international trade easier. When you convert units by hand is where errors creep in; that's why a reliable calculator isn't a luxury.

Fun facts that work well on social media

• The meter was meant to be "natural": one ten-millionth of the meridian quadrant.
• The "master kilo" in Paris was the mass standard for 130 years, until 2019.
• Only three countries haven't officially adopted SI: the United States, Liberia and Myanmar.
• The nautical mile (1852 m) was defined as one minute of latitude — which is why it survives in aviation and shipping, where the Earth matters more than the system.
• The US has "officially" used SI since 1866 for science and international trade… but on the street, everything is imperial.

FAQ about the metric system

Who invented the metric system?

It was commissioned by the French National Assembly in 1791, with scientists like Borda, Lagrange and Laplace involved.

Which country doesn't use the metric system?

The United States is the big case; also Liberia and Myanmar to varying degrees.

Is the meter defined by the meridian?

Not anymore: since 1983 it's the distance light travels in a vacuum in 1/299,792,458 seconds.

When did the US adopt the metric system?

It never fully did for daily life: SI is legal and used in science since 1866, but imperial remains the everyday standard.

Why does the US still use imperial?

Historical inertia and transition costs: changing every sign, label and tool would cost billions.

Want to convert between historical and modern systems? Use the unit calculator — meters, feet, pounds, kilos and more, instantly.

You bought a 500 GB drive, plugged it in, and Windows says it has 465 GB. Were you scammed? No. It's the difference between the decimal system (KB, MB, GB) and the binary one (KiB, MiB, GiB) — and understanding it saves you surprises every time you buy storage.

Decimal vs binary: the two ways of counting bytes

• Decimal (SI): 1 KB = 1000 bytes. Used by drive, USB stick and SD card manufacturers, and by internet speeds.
• Binary (IEC): 1 KiB = 1024 bytes. Used by operating systems when showing files and by RAM sizes.

Neither is "wrong": they're two conventions. The problem is that manufacturers advertise in decimal while your operating system displays in binary (even though it labels it GB).

Quick table: KB vs KiB, MB vs MiB

The 500 GB drive case, explained

A 500 GB drive (decimal) holds 500 × 10⁹ = 500,000,000,000 bytes. Windows divides that by 2³⁰ (1,073,741,824) and gets 465.66 → it shows 465 GB (actually GiB). Nobody tricked you: it's just two ways of counting the same bytes.

Why it matters in practice

The gap grows with every scale:

• A 1 TB drive (decimal) shows 931 GiB.
• A 2 TB drive shows 1.81 TiB.
• SD cards, USB sticks and cloud storage: exactly the same.

Trick: to know the real space your system will show, multiply decimal TB by 0.931 (or GB by 0.931). A "1 TB" drive is really 931 GiB usable.

Internet speeds: another disguised decimal

Providers advertise 300 Mb/s, but those are megabits, not megabytes: 300 Mb/s ÷ 8 = 37.5 MB/s actual download speed. And those "megs" are decimal (1 Mb = 1,000,000 bits), just like drives. That's why you never download at the "advertised" speed: first you divide by 8 (bits → bytes), and on top of that your OS counts in binary.

Common KB and KiB mistakes

• Assuming 1 MB = 1024 KB: in decimal it's 1000, in binary 1024. Depends on who labels it.
• Mixing notations: 1 MB ≠ 1 MiB. They differ by 2.4 % at the MB scale, 7.4 % at the GB scale and 10 % at the TB scale.
• Using "megs" for internet speed: there it's always decimal and in bits, not bytes.

FAQ about KB, KiB and storage

How many bytes are in a KiB?

1024 bytes.

Why do manufacturers use decimal?

Because the SI defines the kilo, mega and giga prefixes in base 10 — and the numbers look bigger.

Do I use KB or KiB?

Almost every operating system shows GiB but labels it GB. Now you know how to read it.

How much real space does a 1 TB drive have?

1 TB decimal = 10¹² bytes ≈ 931 GiB visible.

How much do I actually download with 300 Mb/s?

300 ÷ 8 = 37.5 MB/s theoretical; in practice, a bit less.

Convert between KB, KiB, MB, MiB, GB, GiB and more with the unit calculator — no decimal/binary confusion.

Your phone says 25 °C and your friend in New York says "it's 77 degrees." Your new oven only shows Celsius but the recipe says 350 °F. And in the lab or the classroom, everything is in Kelvin.

Celsius, Fahrenheit and Kelvin coexist depending on the country and context: weather, cooking, science or programming. Converting between them is easy if you remember two base formulas and a couple of reference points. Here they are, with examples and the mistakes to avoid.

The temperature conversion formulas

• C → F: F = C × 9/5 + 32
• F → C: C = (F − 32) × 5/9
• C → K: K = C + 273.15
• K → C: C = K − 273.15

Important detail: Kelvin doesn't use the degree symbol in modern notation (you write 300 K, not 300 °K) and can't be negative: 0 K is absolute zero, the theoretical limit of cold.

Quick temperature reference table

Practical temperature conversion examples

• Weather: 25 °C → 25 × 9/5 + 32 = 77 °F. Correct: "it's 77 degrees."
• Oven: 350 °F → (350 − 32) × 5/9 ≈ 176.7 °C, the classic medium oven.
• Science: 0 K (absolute zero) → −273.15 °C. Water boils at 373.15 K at sea level.
• Fever: 98.6 °F → (98.6 − 32) × 5/9 = 37 °C, normal body temperature.

Oven temperatures: the table that saves your recipes

American ovens use Fahrenheit and European recipes use Celsius. Memorize these equivalents:

Quick trick: every 10 °C is 18 °F. But don't try shortcuts like "180 + 32": that gives 212 °F and it's wrong. The full formula: (180 × 9/5) + 32 = 356 °F, which in practice rounds to 350 °F.

Reference temperatures in science

• 0 K (−273.15 °C): absolute zero, the theoretical limit of cold.
• 77 K (−196 °C): boiling point of liquid nitrogen.
• 273.15 K (0 °C): freezing point of water.
• 373.15 K (100 °C): boiling point of water at sea level.

Common temperature conversion mistakes

• Forgetting to subtract 32 before multiplying when going from F to C (mistake #1).
• Adding 273.15 instead of subtracting it when going from K to C.
• Thinking 100 °C and 212 °F are different temperatures: they're the same, just on different scales.
• Using the "double and add 30" trick for science: fine for weather, not for precision.

FAQ about temperature conversion

At what temperature do Celsius and Fahrenheit meet?

At −40°: −40 °C = −40 °F.

How many degrees Celsius is 98.6 °F?

37 °C, normal body temperature.

When should I use Kelvin?

In science and technology; 0 K is absolute zero and there are no negative temperatures in Kelvin.

What is 350 °F in Celsius?

(350 − 32) × 5/9 ≈ 176.7 °C, the classic medium oven.

How do I convert Celsius to Fahrenheit mentally?

Double and add 30: 20 °C → 70 °F (exact: 68). Good for weather, not for science.

Convert any temperature instantly with the unit calculator — Celsius, Fahrenheit and Kelvin in seconds.