How to use the temperature converter
- Type a temperature into any of the five boxes: Celsius, Fahrenheit, Kelvin, Rankine or Réaumur.
- Read the other four instantly. The line underneath shows the working, the nearest oven gas mark for cooking temperatures, and a note for body temperatures.
- Use the quick buttons for common reference points, or print the chart below to stick on the fridge.
Temperature conversion formulas
| Conversion | Formula | Worked example |
|---|---|---|
| Celsius to Fahrenheit | °F = °C × 9/5 + 32 | 30 °C × 1.8 = 54; 54 + 32 = 86 °F |
| Fahrenheit to Celsius | °C = (°F − 32) × 5/9 | (100 °F − 32) = 68; 68 × 5/9 = 37.8 °C |
| Celsius to Kelvin | K = °C + 273.15 | 25 °C + 273.15 = 298.15 K |
| Kelvin to Celsius | °C = K − 273.15 | 77 K − 273.15 = −196.15 °C (liquid nitrogen) |
| Fahrenheit to Kelvin | K = (°F + 459.67) × 5/9 | (32 + 459.67) × 5/9 = 273.15 K |
| Fahrenheit to Rankine | °R = °F + 459.67 | 70 °F + 459.67 = 529.67 °R |
| Celsius to Réaumur | °Ré = °C × 4/5 | 100 °C × 0.8 = 80 °Ré |
Why 9/5? Water freezes at 0 °C / 32 °F and boils at 100 °C / 212 °F, so 100 Celsius degrees span 180 Fahrenheit degrees: each Celsius degree is 1.8 Fahrenheit degrees. The +32 shifts the zero point. A temperature difference converts without the 32: a rise of 10 °C is a rise of 18 °F.
Celsius to Fahrenheit chart
From −40 °C (where the scales meet) to 250 °C, in 5-degree steps up to boiling and 10-degree steps for cooking temperatures. Use the Print C ↔ F chart button to print just these tables.
| °C | °F | °C | °F | °C | °F |
|---|---|---|---|---|---|
| −40 °C | −40 °F | 35 °C | 95 °F | 120 °C | 248 °F |
| −35 °C | −31 °F | 40 °C | 104 °F | 130 °C | 266 °F |
| −30 °C | −22 °F | 45 °C | 113 °F | 140 °C | 284 °F |
| −25 °C | −13 °F | 50 °C | 122 °F | 150 °C | 302 °F |
| −20 °C | −4 °F | 55 °C | 131 °F | 160 °C | 320 °F |
| −15 °C | 5 °F | 60 °C | 140 °F | 170 °C | 338 °F |
| −10 °C | 14 °F | 65 °C | 149 °F | 180 °C | 356 °F |
| −5 °C | 23 °F | 70 °C | 158 °F | 190 °C | 374 °F |
| 0 °C | 32 °F | 75 °C | 167 °F | 200 °C | 392 °F |
| 5 °C | 41 °F | 80 °C | 176 °F | 210 °C | 410 °F |
| 10 °C | 50 °F | 85 °C | 185 °F | 220 °C | 428 °F |
| 15 °C | 59 °F | 90 °C | 194 °F | 230 °C | 446 °F |
| 20 °C | 68 °F | 95 °C | 203 °F | 240 °C | 464 °F |
| 25 °C | 77 °F | 100 °C | 212 °F | 250 °C | 482 °F |
| 30 °C | 86 °F | 110 °C | 230 °F |
Fahrenheit to Celsius chart
| °F | °C | °F | °C |
|---|---|---|---|
| −20 °F | −28.9 °C | 0 °F | −17.8 °C |
| 10 °F | −12.2 °C | 20 °F | −6.7 °C |
| 32 °F | 0 °C | 40 °F | 4.4 °C |
| 50 °F | 10 °C | 60 °F | 15.6 °C |
| 70 °F | 21.1 °C | 80 °F | 26.7 °C |
| 90 °F | 32.2 °C | 98.6 °F | 37 °C |
| 100 °F | 37.8 °C | 110 °F | 43.3 °C |
| 150 °F | 65.6 °C | 200 °F | 93.3 °C |
| 212 °F | 100 °C | 250 °F | 121.1 °C |
| 300 °F | 148.9 °C | 350 °F | 176.7 °C |
| 400 °F | 204.4 °C | 450 °F | 232.2 °C |
| 500 °F | 260 °C |
Oven temperatures and gas marks
| Gas mark | °C (conventional) | °C (fan / convection) | °F | Description |
|---|---|---|---|---|
| ¼ | 110 | 90 | 225 | Very cool: meringues, drying |
| ½ | 120 | 100 | 250 | Very cool |
| 1 | 140 | 120 | 275 | Cool: slow cooking, custards |
| 2 | 150 | 130 | 300 | Cool: fruit cakes |
| 3 | 170 | 150 | 325 | Moderate: casseroles |
| 4 | 180 | 160 | 350 | Moderate: most cakes and biscuits |
| 5 | 190 | 170 | 375 | Moderately hot |
| 6 | 200 | 180 | 400 | Hot: roast vegetables, bread |
| 7 | 220 | 200 | 425 | Hot: roasting, pastry |
| 8 | 230 | 210 | 450 | Very hot |
| 9 | 240 | 220 | 475 | Very hot: pizza, flatbreads |
| 10 | 260 | 240 | 500 | Hottest domestic setting |
Gas mark tables are conventional rounded equivalents rather than exact conversions, and recipes round to convenient numbers, so 350 °F becomes 180 °C rather than 176.7 °C. For fan or convection ovens, lower the temperature by about 20 °C (25 °F) or shorten the cooking time. Oven thermostats are often 10–20 degrees off; an inexpensive oven thermometer is the most reliable fix.
Body temperature and fever
| Range | °C | °F |
|---|---|---|
| Hypothermia | below 35.0 | below 95.0 |
| Typical normal (varies by person and time of day) | 36.1 – 37.2 | 97.0 – 99.0 |
| Fever | 38.0 or higher | 100.4 or higher |
| High fever | 39.4 or higher | 103.0 or higher |
| Very high: seek urgent care | 40.0 or higher | 104.0 or higher |
Readings depend on where they are taken: rectal and ear readings run a little higher than oral readings, and underarm readings lower. This is general information, not medical advice; for infants under three months, any reading of 38 °C (100.4 °F) or more warrants a call to a doctor.
Everyday reference points
| Reference | °C | °F | K |
|---|---|---|---|
| Absolute zero | −273.15 | −459.67 | 0 |
| Celsius equals Fahrenheit | −40 | −40 | 233.15 |
| Home freezer | −18 | 0 | 255.15 |
| Water freezes (sea level) | 0 | 32 | 273.15 |
| Refrigerator | 4 | 39 | 277.15 |
| Comfortable room | 20 – 22 | 68 – 72 | 293 – 295 |
| Hot summer day | 35 | 95 | 308.15 |
| Safe internal temperature: whole cuts of beef and pork (then rest 3 min) | 63 | 145 | 336 |
| Safe internal temperature: poultry | 74 | 165 | 347 |
| Water boils (sea level) | 100 | 212 | 373.15 |
| Sugar: soft-ball stage | 112 – 116 | 235 – 240 | – |
| Deep frying | 175 – 190 | 350 – 375 | – |
Water boils at a lower temperature at altitude, about 1 °C less for every 300 m, which is why high-altitude recipes need adjusting.
Kelvin, Rankine and Réaumur
Kelvin is the SI unit of temperature and starts at absolute zero, where particles have the least possible thermal energy. One kelvin is the same size as one Celsius degree, and it is written without a degree sign (300 K, not 300 °K). Scientists use it because ratios make sense on an absolute scale: 600 K is twice as hot, in energy terms, as 300 K. Rankine does the same for Fahrenheit-sized degrees and appears in US thermodynamics and HVAC calculations. Réaumur, from 1730, divides the freezing-to-boiling range into 80 degrees; it was common in Europe until the 19th century. For other measurement conversions, the unit converter covers 19 categories including pressure, energy and volume.
Frequently asked questions
How do I convert Celsius to Fahrenheit?
Multiply the Celsius temperature by 9/5 (1.8) and add 32. For example, 25 °C × 1.8 = 45, plus 32 = 77 °F. A quick mental estimate is to double the Celsius value and add 30, which is close for everyday weather.
How do I convert Fahrenheit to Celsius?
Subtract 32 from the Fahrenheit temperature, then multiply by 5/9. For example, 68 °F − 32 = 36, and 36 × 5/9 = 20 °C. For a rough estimate, subtract 30 and halve.
At what temperature are Celsius and Fahrenheit the same?
−40. Setting C = C × 9/5 + 32 gives C = −40, so −40 °C and −40 °F are the same temperature.
What is 350 °F in Celsius for an oven?
350 °F is 176.7 °C, which recipes round to 180 °C, or gas mark 4. In a fan (convection) oven, reduce it to about 160 °C.
What body temperature is a fever?
For adults, a temperature of 38 °C (100.4 °F) or higher is generally considered a fever; normal is roughly 36.1–37.2 °C (97–99 °F) and varies by person, time of day and where it is measured. For babies under 3 months, any temperature of 38 °C or more needs prompt medical advice.
How do I convert Celsius to Kelvin?
Add 273.15. 0 °C is 273.15 K and 100 °C is 373.15 K. Kelvin has no degree sign and no negative values, because 0 K is absolute zero.
What are Rankine and Réaumur?
Rankine is an absolute scale with Fahrenheit-sized degrees, used in some US engineering: °R = °F + 459.67. Réaumur is a historical scale where water freezes at 0 and boils at 80; it survives in some European cheese and sugar making.