Unit & Measurement Tables
Temperature Conversion Table
Temperature is the only common conversion that is not a simple multiplication. Celsius and Fahrenheit have different zero points as well as different step sizes, so you cannot scale one into the other — you have to scale and then shift. That single difference explains why almost every temperature conversion error is off by exactly 32 or by a factor of 1.8.
The relationship is exact and linear: F = C × 1.8 + 32, and the inverse is C = (F − 32) ÷ 1.8. Kelvin uses the same step size as Celsius but starts at absolute zero, so K = C + 273.15. There is no rounding anywhere in these three equations — they are definitions, not approximations.
The tables below cover three different jobs. The first is for weather and science, where you want a value and its Kelvin equivalent. The second is for reading a US forecast or an American recipe. The third is for the kitchen, because oven dials in the UK are marked in gas marks while US recipes give Fahrenheit and European ones give Celsius, and the three do not line up neatly.
Celsius to Fahrenheit and Kelvin
| Celsius | Fahrenheit | Kelvin |
|---|---|---|
| -40 | -40 | 233.15 |
| -20 | -4 | 253.15 |
| -10 | 14 | 263.15 |
| 0 | 32 | 273.15 |
| 5 | 41 | 278.15 |
| 10 | 50 | 283.15 |
| 15 | 59 | 288.15 |
| 20 | 68 | 293.15 |
| 25 | 77 | 298.15 |
| 30 | 86 | 303.15 |
| 35 | 95 | 308.15 |
| 37 | 98.6 | 310.15 |
| 40 | 104 | 313.15 |
| 50 | 122 | 323.15 |
| 60 | 140 | 333.15 |
| 80 | 176 | 353.15 |
| 100 | 212 | 373.15 |
| 150 | 302 | 423.15 |
| 200 | 392 | 473.15 |
| 250 | 482 | 523.15 |
| 300 | 572 | 573.15 |
−40 is the only temperature where Celsius and Fahrenheit read the same. 37 °C is body temperature; 100 °C is water boiling at sea level.
Fahrenheit to Celsius
| Fahrenheit | Celsius | Kelvin | What it feels like |
|---|---|---|---|
| 0 | -17.8 | 255.37 | Below freezing — exposed skin at risk |
| 20 | -6.7 | 266.48 | Freezing |
| 32 | 0 | 273.15 | Freezing |
| 40 | 4.4 | 277.59 | Cold — coat weather |
| 50 | 10 | 283.15 | Cold — coat weather |
| 68 | 20 | 293.15 | Mild — comfortable |
| 80 | 26.7 | 299.82 | Warm — shorts weather |
| 98.6 | 37 | 310.15 | Very hot — heat illness risk |
| 100 | 37.8 | 310.93 | Very hot — heat illness risk |
| 150 | 65.6 | 338.71 | Very hot — heat illness risk |
| 200 | 93.3 | 366.48 | Very hot — heat illness risk |
| 212 | 100 | 373.15 | Very hot — heat illness risk |
| 250 | 121.1 | 394.26 | Very hot — heat illness risk |
| 300 | 148.9 | 422.04 | Very hot — heat illness risk |
| 350 | 176.7 | 449.82 | Very hot — heat illness risk |
| 400 | 204.4 | 477.59 | Very hot — heat illness risk |
| 450 | 232.2 | 505.37 | Very hot — heat illness risk |
| 500 | 260 | 533.15 | Very hot — heat illness risk |
The description column is a rough guide for outdoor air, not a physical property.
Oven temperatures, Celsius to Fahrenheit and gas mark
| Celsius | Fahrenheit | Gas mark | Typical use |
|---|---|---|---|
| 110 | 230 | ¼ | Slow — meringue, drying |
| 140 | 284 | 1 | Very low — slow roast |
| 150 | 302 | 2 | Low — custards, rich fruit cake |
| 170 | 338 | 3 | Moderate — biscuits, traybake |
| 180 | 356 | 4 | Moderate — cakes, most baking |
| 190 | 374 | 5 | Moderately hot — pastry, bread |
| 200 | 392 | 6 | Hot — roasting, Yorkshire pudding |
| 220 | 428 | 7 | Very hot — pizza, crisp roast potatoes |
| 230 | 446 | 8 | Very hot — fast browning |
| 240 | 464 | 9 | Hottest — charring, naan |
Gas marks are a UK convention. Fan-assisted ovens typically need 20 °C lower than the conventional figure shown here.
How to Use These Tables
- Celsius to Fahrenheit: double the Celsius value, subtract 10% of the result, then add 32. For 20 °C that is 40, minus 4, plus 32 — 68 °F, which is exact.
- Fahrenheit to Celsius: subtract 32 first, then divide by 1.8. Doing it in the other order is the single most common mistake.
- Never convert a temperature difference the same way as a temperature. A 10 °C rise is an 18 °F rise — no 32 offset, because the zero points cancel.
- For oven temperatures, use the third table rather than converting a gas mark arithmetically; the marks are rounded by design, not derived.
Common Questions
Why is -40 the same in Celsius and Fahrenheit?
Because it is the one point where the two scales cross. Solving C = C × 1.8 + 32 gives C = −40. Below that, Fahrenheit reads lower than Celsius; above it, Fahrenheit reads higher.
Is 100 °F a fever?
100 °F is 37.8 °C, which is a low-grade fever — normal body temperature is about 37 °C or 98.6 °F. The usual clinical threshold is 38 °C, or 100.4 °F.
Why does Kelvin have no degree symbol?
Kelvin is an absolute scale, so its unit is written as K rather than °K. It also starts at absolute zero, which is why 0 °C is 273.15 K and not zero.
Can I convert a temperature range by just converting the endpoints?
Yes, for the endpoints, but not by applying the +32 offset to the range itself. A range of 20–30 °C is 68–86 °F; the range is 10 °C or 18 °F, not 50 °F.
What is 180 °C in a fan oven?
A conventional oven at 180 °C is about 160 °C in a fan oven, because the fan moves heat more efficiently. US recipes quoting 350 °F correspond to 180 °C conventional or 160 °C fan.
More Unit & Measurement Tables
Sources
- The International System of Units (SI Brochure), 9th edition — kelvin — Bureau International des Poids et Mesures
- NIST Special Publication 811 — Guide for the Use of the International System of Units — National Institute of Standards and Technology
- NIST Guide to the SI, Chapter 9 — Temperature — National Institute of Standards and Technology
Filed with Unit Conversion calculations.