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
| Celsius | Fahrenheit | Kelvin |
|---|---|---|
| −40 | −40 | 233.15 |
| 0 | 32 | 273.15 |
| 10 | 50 | 283.15 |
| 20 | 68 | 293.15 |
| 37 | 98.6 | 310.15 |
| 100 | 212 | 373.15 |
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:
| Use | °C | °F |
|---|---|---|
| Low oven | 150 | 300 |
| Medium oven | 180 | 350 |
| Hot oven | 200 | 400 |
| Very hot | 230 | 450 |
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.
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