What this does
Converts a Celsius temperature to Fahrenheit as you type. The formula is °F = °C × 9/5 + 32: multiply by 1.8, then add 32. The page opens at 20 °C, a typical room temperature, showing 68 °F. Either box is editable — type Fahrenheit on the right and the Celsius side recomputes — and the ⇄ button swaps the two scales while keeping the left-hand number. Results are rounded to six decimal places, though a Celsius value with one decimal always gives a Fahrenheit figure with at most two. It runs in the browser and works offline.
What is the formula for Celsius to Fahrenheit?
°F = °C × 9/5 + 32. Two things happen: a Celsius degree is 1.8 times the size of a Fahrenheit degree, so the number is scaled up, and the scales put zero in different places (Celsius at freezing, Fahrenheit 32 degrees below it), so 32 is added afterwards. Multiply before you add — 25 °C is 45 + 32 = 77 °F, not 1.8 × 57. Worked example with the tool's rounding: a thermometer reading of 36.6 °C is 36.6 × 1.8 = 65.88, plus 32 = 97.88 °F, and that's exactly what the tool displays.
Celsius to Fahrenheit at a glance
| °C | °F | Feels like |
|---|---|---|
| −18 | −0.4 | a domestic freezer |
| 0 | 32 | water freezes |
| 10 | 50 | jacket weather |
| 21 | 69.8 | a European thermostat default |
| 30 | 86 | a hot day in London or Berlin |
| 37 | 98.6 | normal body temperature |
| 100 | 212 | water boils at sea level |
| 180 | 356 | a moderate oven |
How do I convert °C to °F in my head?
Double it and add 30. 20 °C → 40 + 30 = 70 °F (real 68); 30 °C → 90 (real 86). The shortcut runs a couple of degrees warm above 10 °C and a couple cool below it, because the true multiplier is 1.8 rather than 2. For a tighter version, double it, subtract a tenth of that, then add 32: 30 °C → 60 − 6 + 32 = 86, which is exact.
What Fahrenheit setting matches a 180 °C recipe?
Most European and Australian recipes bake at 160, 180, or 200 °C. Those are 320, 356, and 392 °F. US oven dials step in 25s, so set 325, 350, and 400 °F respectively — the nearest notch, and within 8 °F of the target. 220 °C for roasting is 428 °F, so use 425; 230 °C for bread is 446 °F, so use 450. If the recipe specifies a fan oven, add about 20 °C before converting, because fan temperatures are quoted lower.
Is 38 °C a fever in Fahrenheit?
Yes. 38 °C is 100.4 °F, which is the threshold most US clinics and school policies use. 37.5 °C is 99.5 °F, 39 °C is 102.2 °F, and 40 °C is 104 °F. Because a Celsius degree is bigger, a child's temperature quoted "in tenths" in Celsius is more precise than the same number of decimals in Fahrenheit; if a US doctor asks for the reading, give them 100.4 rather than rounding 38 to "100".
Where do both scales show the same number?
At −40: −40 °C × 1.8 = −72, plus 32 = −40 °F. Type −40 into the left box to see it. It's the only point where the two lines cross, so "forty below" needs no unit. Kelvin is also in the dropdowns here (K = °C + 273.15), and the reverse direction has its own page at Fahrenheit to Celsius; every other unit lives in the full converter.