How to use the Celsius to Fahrenheit converter
Enter the temperature, choose the direction and read the result. Kelvin is shown in every case, and when the value is a well-known reference point — freezing, boiling, normal body temperature, the usual fever threshold — the converter says so.
The formulas
Celsius and Fahrenheit differ in two ways: where zero sits (water freezes at 0 °C but 32 °F) and how big a degree is (100 Celsius degrees span the same range as 180 Fahrenheit degrees, so one Celsius degree is 1.8 Fahrenheit degrees). Both differences appear in the formula:
- °F = °C × 9/5 + 32
- °C = (°F − 32) × 5/9
- K = °C + 273.15 (Kelvin starts at absolute zero and has the same degree size as Celsius)
The order matters: multiply first, then add 32 when going to Fahrenheit; subtract 32 first, then multiply when coming back.
Worked example: 20 °C
20 × 9/5 = 36, and 36 + 32 = 68 °F — a pleasant spring day. Checking the reverse: (68 − 32) × 5/9 = 36 × 5/9 = 20 °C. In Kelvin, 20 + 273.15 = 293.15 K.
The mental shortcut and its error
For weather, double the Celsius and add 30. 20 °C → 40 + 30 = 70 °F, against the exact 68 °F. The shortcut multiplies by 2 instead of 1.8 and adds 30 instead of 32, so it is exact at 10 °C (50 °F) and drifts by 2 °F for every 10 °C away from there: 30 °C gives 90 instead of 86, and 0 °C gives 30 instead of 32. Going the other way, subtract 30 and halve: 86 °F → 56 ÷ 2 = 28 °C (exact: 30 °C). Fine for packing a suitcase, not for a recipe or a thermostat.
Weather temperatures
| °C | °F |
|---|---|
| -30 | -22 |
| -25 | -13 |
| -20 | -4 |
| -15 | 5 |
| -10 | 14 |
| -5 | 23 |
| 0 | 32 |
| 5 | 41 |
| 10 | 50 |
| 15 | 59 |
| 20 | 68 |
| 25 | 77 |
| 30 | 86 |
| 35 | 95 |
| 40 | 104 |
| 45 | 113 |
Handy anchors: 0 °C is freezing, 10 °C (50 °F) is jacket weather, 20 °C (68 °F) is room temperature in most homes, 30 °C (86 °F) is hot, and 40 °C (104 °F) is dangerous heat.
Oven temperatures
| °C | °F |
|---|---|
| 120 | 248 |
| 130 | 266 |
| 140 | 284 |
| 150 | 302 |
| 160 | 320 |
| 170 | 338 |
| 180 | 356 |
| 190 | 374 |
| 200 | 392 |
| 210 | 410 |
| 220 | 428 |
| 230 | 446 |
| 240 | 464 |
| 250 | 482 |
Recipes often round: a "180 °C" oven is 356 °F, which US recipes write as 350 °F; "200 °C" is 392 °F, written as 400 °F. Home ovens are rarely accurate to better than 10 degrees either way, so these roundings do no harm. Fan (convection) ovens usually call for about 20 °C less than the conventional figure.
Body temperature
| °C | °F |
|---|---|
| 35 | 95 |
| 36 | 96.8 |
| 36.5 | 97.7 |
| 37 | 98.6 |
| 37.5 | 99.5 |
| 38 | 100.4 |
| 38.5 | 101.3 |
| 39 | 102.2 |
| 40 | 104 |
| 41 | 105.8 |
The classic "normal" of 37 °C is 98.6 °F; real readings vary by person, time of day and where the thermometer is placed. A reading of 38 °C (100.4 °F) is the figure most commonly used as the start of a fever. Thermometer readings are a guide only — when to call a doctor depends on age, symptoms and medical history, not on one number.
Tips
- Negative temperatures work the same way: −10 °C × 1.8 + 32 = 14 °F. The two scales cross at −40.
- Temperature differences convert without the 32: a rise of 5 °C is a rise of 9 °F.
- Weather apps, car dashboards and thermostats can be switched between °C and °F in their settings; for everything else, the unit converter handles temperature alongside length, weight and volume.
Frequently asked questions
How do I convert Celsius to Fahrenheit?
Multiply by 1.8 (that is 9/5) and add 32. 25 °C × 1.8 = 45, plus 32 = 77 °F.
How do I convert Fahrenheit to Celsius?
Subtract 32, then multiply by 5/9. 77 °F − 32 = 45, × 5/9 = 25 °C. For a quick estimate, subtract 30 and halve.
What is 37 degrees Celsius in Fahrenheit?
37 °C is 98.6 °F, the traditional figure for normal body temperature. 38 °C is 100.4 °F, the value commonly used as the threshold for a fever.
What is 180 °C in Fahrenheit for baking?
180 °C is 356 °F. American recipes round this to 350 °F; the small difference is well within an ordinary oven’s accuracy.
At what temperature are Celsius and Fahrenheit equal?
At −40: −40 °C × 1.8 + 32 = −40 °F. It is the only point where the two scales give the same number.
Last updated: October 9, 2026