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
| From | To | Factor |
|---|---|---|
| 1 m | cm | × 100 |
| 1 m | mm | × 1000 |
| 1 km | m | × 1000 |
| 1 inch (in) | cm | × 2.54 |
| 1 foot (ft) | m | × 0.3048 |
| 1 yard (yd) | m | × 0.9144 |
| 1 mile (mi) | km | × 1.609344 |
| 1 nautical mile | km | × 1.852 |
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.
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