Temperature is the one unit where the numbers themselves are meaningless until you know the context. "100" is a fever in Celsius, a perfect roast in Fahrenheit, and "boiling" in neither scale's daily use. This guide maps the numbers that matter in cooking and weather onto both scales.
The scales in 30 seconds
Celsius anchors water: 0 freeze, 100 boil, 20-25 comfortable room. Fahrenheit anchors the human experience: 0 is bitterly cold, 100 is dangerously hot, 98.6 is body temperature. Kelvin is Celsius shifted by 273.15; it appears in science and nowhere in a kitchen.
The exact formulas: °F = °C × 9/5 + 32, °C = (°F - 32) × 5/9, K = °C + 273.15. Or use the °C → °F converter and skip the arithmetic.
Oven settings, converted
| Setting | °F | °C | Gas mark | Fan oven |
|---|---|---|---|---|
| Very low / meringues | 225 | 110 | 1/4 | 90 |
| Low / slow braise | 300 | 150 | 2 | 130 |
| Moderate / cakes | 350 | 175-180 | 4 | 160 |
| Hot / bread, roast veg | 425 | 220 | 7 | 200 |
| Very hot / pizza | 475-500 | 245-260 | 9 | 230 |
Convection rule: reduce the setting by 20 °C / 25 °F when the recipe was written for conventional heat, unless the recipe already specifies fan.
Safe doneness temperatures (US FDA)
| Food | °F | °C |
|---|---|---|
| Poultry (all), ground meats | 165 | 74 |
| Whole pork, chops | 145 + rest | 63 |
| Whole beef/lamb (medium-rare) | 135 | 57 |
| Fish (flakes, opaque) | 145 | 63 |
Carry-over heat adds 2-5 degrees after resting; pull meat a few degrees early.
Body temperature
- Normal: 36.5-37.5 °C (97.7-99.5 °F), varies by person and time of day
- Fever: ≥ 38 °C = 100.4 °F (the ".4" is exact, from converting 38.0)
- High fever: ≥ 39.5 °C (103.1 °F): call a doctor
- Hypothermia: < 35 °C (95 °F): emergency
The common mistake: treating "100 °F" as automatically worrying. It is 37.8 °C, barely a fever. The unit is doing the scaring.
Reading weather in both scales
| °C | °F | What it feels like |
|---|---|---|
| -10 | 14 | Real winter coat |
| 0 | 32 | Freezing, ice risk |
| 10 | 50 | Jacket weather |
| 20 | 68 | Comfortable |
| 30 | 86 | Hot, seek shade |
| 40 | 104 | Dangerous heat |
The ±2-degree mental shortcut (double the Celsius, add 30) is accurate enough for dressing decisions across the entire livable range. Use the converter when precision matters: ovens, fevers, fermentation, candy stages.