The formulas
celsius = (fahrenheit - 32) x 5 / 9
fahrenheit = celsius x 9 / 5 + 32
Both are exact. Water freezes at 32 °F and 0 °C and boils at 212 °F and 100 °C at sea level, so the same span is 180 Fahrenheit degrees but only 100 Celsius degrees. That is where 5/9 (or 9/5, which is 1.8) comes from, and 32 lines up the two freezing points.
- Rounding. The converter shows one decimal place and drops a trailing .0, so 212 °F reads 100 °C and 350 °F reads 176.7 °C.
- A rough figure in your head. Doubling the Celsius and adding 30 gets close for weather: 20 °C gives 70 °F against an exact 68 °F. It drifts as the numbers rise, and 200 °C gives 430 °F against an exact 392 °F, so use the formula for ovens and meat.
Quick chart
| Fahrenheit | °C |
|---|---|
| -40 °F (same on both scales) | -40 |
| 0 °F | -17.8 |
| 32 °F | 0 |
| 100 °F | 37.8 |
| 212 °F | 100 |
| 250 °F | 121.1 |
| 300 °F | 148.9 |
| 325 °F | 162.8 |
| 350 °F | 176.7 |
| 375 °F | 190.6 |
| 400 °F | 204.4 |
| 425 °F | 218.3 |
| 450 °F | 232.2 |
-40 is the one point where the two scales meet: -40 °F is exactly -40 °C.
| Celsius | °F |
|---|---|
| -18 °C | -0.4 |
| 0 °C | 32 |
| 20 °C | 68 |
| 37 °C | 98.6 |
| 100 °C | 212 |
| 150 °C | 302 |
| 160 °C | 320 |
| 180 °C | 356 |
| 200 °C | 392 |
| 220 °C | 428 |
| 230 °C | 446 |
| 250 °C | 482 |
Reference temperatures
| Reference point | °F | °C | Source |
|---|---|---|---|
| Water freezes | 32 | 0 | NIST Metric Kitchen |
| Water boils (at sea level) | 212 | 100 | NIST Metric Kitchen |
| Beef, pork, veal and lamb steaks, roasts and chops, then a 3-minute rest | 145 | 62.8 | USDA Food Safety and Inspection Service |
| Fish | 145 | 62.8 | USDA Food Safety and Inspection Service |
| Ground beef, pork, veal and lamb | 160 | 71.1 | USDA Food Safety and Inspection Service |
| Egg dishes | 160 | 71.1 | USDA Food Safety and Inspection Service |
| Poultry, whole or ground | 165 | 73.9 | USDA Food Safety and Inspection Service |
| Leftovers and casseroles | 165 | 73.9 | USDA Food Safety and Inspection Service |
The meat, fish, egg and leftover figures come from the USDA Food Safety and Inspection Service's Safe Minimum Internal Temperature Chart, and they are internal temperatures, measured with a food thermometer. The Celsius column is the exact conversion of the Fahrenheit figures; rounded to the whole degree, 145 °F is 63 °C, 160 °F is 71 °C and 165 °F is 74 °C. The 3-minute rest applies to whole cuts of beef, pork, veal and lamb, not to ground meat. The water figures are from NIST's metric kitchen.
Below zero
Minus numbers work in both boxes. The lowest the converter accepts is absolute zero, -459.67 °F or -273.15 °C, which is 0 on the kelvin scale and the coldest temperature there is. NIST Special Publication 811 gives both figures in its conversion rules.
Oven settings
For gas marks and fan ovens, use the oven temperature converter.