How to convert Fahrenheit to Celsius
Example: 98.6 °F − 32 = 66.6, × 5/9 = 37 °C — normal body temperature. The order matters: subtract the 32 offset first, then scale. Mental shortcut: subtract 30 and halve — 98.6 → 68.6 → ~34; it reads a few degrees low at body heat but is solid for weather.
°F to °C conversion chart
| °F | °C | Context |
|---|---|---|
| 0 | -17.8 | Bitter cold — a US winter storm |
| 32 | 0 | Freezing point of water |
| 50 | 10 | Cool spring day |
| 68 | 20 | Room temperature |
| 77 | 25 | Warm afternoon |
| 86 | 30 | Hot day |
| 98.6 | 37 | Body temperature |
| 100.4 | 38 | Fever threshold |
| 212 | 100 | Boiling water |
| 350 | 176.7 | Standard baking (≈ 180 °C) |
| 425 | 218.3 | Roasting / pizza (≈ 220 °C) |
Reading American temperatures
A rough map for °F: below 32 is freezing, 50s are cool, 70s are pleasant, 90s are hot, 100+ is a heatwave. For health: US thermometers call 100.4 °F a fever — exactly 38 °C. For cooking, US recipes bake at 350 °F (≈ 180 °C) and roast at 400–425 °F (≈ 200–220 °C); converting and rounding to the nearest 10 °C is standard practice.
Sanity checks
Two anchors catch most mistakes: 32 °F must give exactly 0 °C, and −40° must equal −40°. If your hand calculation misses either, the 32 was probably subtracted after multiplying instead of before.
Frequently asked questions
What is the formula for Fahrenheit to Celsius?
Subtract 32, then multiply by 5/9: °C = (°F − 32) × 5/9. For 75 °F: 43 × 5/9 = 23.9 °C.
What is 100 °F in Celsius?
37.8 °C — uncomfortably hot weather, or right below the 38.0 °C fever line if it's a thermometer reading. 100.4 °F is the exact fever threshold.
What is 350 °F in Celsius for baking?
176.7 °C — set a metric oven to 180 °C. The usual pairings: 325→160, 350→180, 375→190, 400→200, 425→220. Fan ovens typically run 20 °C lower than the stated conventional temperature.
Why subtract 32 first?
The two scales have different zero points and different step sizes. Subtracting 32 aligns the zeros (both at water's freezing point); multiplying by 5/9 then fixes the step size. Reversing the order applies the scale factor to the offset too, which is wrong.
Is 0 °F colder than 0 °C?
Much: 0 °F is −17.8 °C — deep-freeze weather — while 0 °C is merely freezing. Zero degrees means very different things on the two scales.