Temperature Converter
Convert Celsius, Fahrenheit and Kelvin exactly, with the formula worked step by step, a weather and cooking reference table and the quick mental shortcuts.
Temperature Converter: with the default inputs, celsius is 37.78 °C.
- Fahrenheit
- 100 °F
- Kelvin
- 310.93 K
- What that feels like
- Human body temperature range.
Assumptions
- Standard Celsius–Fahrenheit–Kelvin relations; the Rankine scale is not shown.
| °C | °F | K | |
|---|---|---|---|
| Absolute zero | -273.2 | -459.7 | 0 |
| °C and °F agree | -40 | -40 | 233.15 |
| Home freezer | -18 | -0.4 | 255.15 |
| Water freezes | 0 | 32 | 273.15 |
| Refrigerator | 4 | 39.2 | 277.15 |
| Cool day | 10 | 50 | 283.15 |
| Room temperature | 21 | 69.8 | 294.15 |
| Hot summer day | 32 | 89.6 | 305.15 |
| Normal body temperature | 37 | 98.6 | 310.15 |
| Fever | 38.5 | 101.3 | 311.65 |
| Hot bath | 40 | 104 | 313.15 |
| Water boils (sea level) | 100 | 212 | 373.15 |
| Slow oven | 150 | 302 | 423.15 |
| Moderate oven | 180 | 356 | 453.15 |
| Hot oven | 220 | 428 | 493.15 |
| Sugar caramelises | 170 | 338 | 443.15 |
How this is worked out
The formula
°F = °C × 9⁄5 + 32 °C = (°F − 32) × 5⁄9 K = °C + 273.15 °F = K × 9⁄5 − 459.67
Open How it’s calculated above to see this worked through with your own numbers.
What you enter
- Temperature
- A number.in °F · defaults to 100
What you get back
- Celsiusmain answer
- Fahrenheit
- Kelvin
- What that feels like
What this assumes
- Standard Celsius–Fahrenheit–Kelvin relations; the Rankine scale is not shown.
About this calculator
Enter a temperature in Celsius, Fahrenheit or Kelvin and the other two update instantly, with the arithmetic shown. Temperature is the one conversion that isn't a simple multiplication — the scales have different zero points as well as different degree sizes — which is why most people can't do it in their head.
The three scales
Celsius sets water's freezing point at 0° and boiling point at 100° (at standard pressure). It's used almost everywhere for weather and science.
Fahrenheit puts freezing at 32° and boiling at 212°, so 180 Fahrenheit degrees span the same range as 100 Celsius degrees — each °F is 5⁄9 of a °C. It survives in the United States and a handful of territories for everyday use.
Kelvin is the SI unit, with the same degree size as Celsius but zero at absolute zero (−273.15 °C), the point where molecular motion is minimal. Scientists use it for anything involving ratios of temperatures (gas laws, radiation). Kelvins are written without a degree sign.
Mental shortcuts
- °C → °F: double it and add 30. 20 °C → 70 °F (exact: 68). Good to within a few degrees for weather.
- °F → °C: subtract 30 and halve it. 80 °F → 25 °C (exact: 26.7).
- Landmarks: 0 °C = 32 °F, 10 = 50, 20 = 68, 30 = 86, 37 = 98.6, 100 = 212, and −40 is the same on both scales.
Body temperature
The traditional "normal" of 37 °C / 98.6 °F comes from 19th-century data; modern studies put the average nearer 36.6 °C (97.9 °F), varying by time of day and person. A fever is usually defined as 38 °C / 100.4 °F or above.
Ovens
Recipes from the UK and Europe give oven temperatures in Celsius (or gas marks); US recipes use Fahrenheit. 180 °C ≈ 350 °F is the workhorse baking temperature; 200 °C ≈ 400 °F for roasting; 220 °C ≈ 425 °F for pizza and bread. Fan ovens usually run about 20 °C hotter than their dial, so recipes say to reduce by 20 °C.
Precision
Results are shown to two decimals. The conversion is exact, so 98.6 °F is exactly 37 °C and 37.0 °C is exactly 98.6 °F.
Frequently asked questions
▸How do I convert Celsius to Fahrenheit?
Multiply by 9, divide by 5, add 32 — or multiply by 1.8 and add 32. 25 °C × 1.8 = 45, + 32 = 77 °F.
▸How do I convert Fahrenheit to Celsius?
Subtract 32, then multiply by 5⁄9. 100 °F − 32 = 68, × 5⁄9 = 37.8 °C.
▸What is normal body temperature in Fahrenheit?
98.6 °F is the traditional figure (37 °C). Modern averages are closer to 97.9 °F, and anything from about 97 to 99 °F is normal. A fever is 100.4 °F (38 °C) and up.
▸At what temperature are Celsius and Fahrenheit equal?
−40. Setting C = F in F = 1.8C + 32 gives C = −40.
▸How do I convert Celsius to Kelvin?
Add 273.15. 25 °C is 298.15 K. There are no negative kelvins; 0 K is absolute zero, −273.15 °C.
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