Temperature Converter
Exact °C, °F and K conversions with the formula worked step by step.
Converts a reading, such as today’s 25 °C. Values below absolute zero (−273.15 °C) are rejected.
Type a temperature in plain words — “37 C to F”, “-40 °F in °C”, “300 K to C” — or use the boxes below.
Exact · °F = °C × 1.8 + 32
- Celsius: °C = K − 273.15 (SI); water freezes at about 0 °C
- Fahrenheit: °F = °C × 1.8 + 32
Working, step by step
25 °C in every unit
Select a unit to convert to it. Values marked ≈ are rounded; all others are exact.
| Unit | Value | Copy |
|---|---|---|
| Common | ||
| from | 25 | |
| to | 77 | |
| 298.15 | ||
| 536.67 | ||
| Historical scales | ||
| 20 | ||
| 20.625 | ||
| 112.5 | ||
| 8.25 | ||
Convert a list of values
Up to 1,000 lines. Fractions (3/4), mixed numbers (1 1/2) and grouped digits (1,250) are fine.
| Value | Result |
|---|
Reference temperatures
Descriptive reference points; the °F and K values are exact conversions of the °C value.
- Absolute zero −273.15 °C −459.67 °F 0 K 0 K by definition; nothing can be colder
- Celsius equals Fahrenheit −40 °C −40 °F 233.15 K the one temperature where both scales agree
- Water freezes (ice point) 0 °C 32 °F 273.15 K at normal atmospheric pressure, very close to 0 °C
- Triple point of water 0.01 °C 32.018 °F 273.16 K ice, liquid water and water vapour in equilibrium
- Average human body temperature 37 °C 98.6 °F 310.15 K the commonly quoted value; a normal temperature varies from person to person and through the day
- Water boils at sea level 100 °C 212 °F 373.15 K about 100 °C at 1 atmosphere; lower at altitude
Common oven settings
Exact equivalents. Recipes usually round them — 180 °C is often paired with 350 °F, although it is exactly 356 °F.
- 140 °C = 284 °F
- 150 °C = 302 °F
- 160 °C = 320 °F
- 170 °C = 338 °F
- 180 °C = 356 °F
- 190 °C = 374 °F
- 200 °C = 392 °F
- 220 °C = 428 °F
- 230 °C = 446 °F
- 250 °C = 482 °F
About the Temperature Converter
Convert a temperature between Celsius, Fahrenheit, kelvin and Rankine, plus the historical Réaumur, Rømer, Delisle and Newton scales. Type in either box and the other updates; every scale is listed in the table underneath and the conversion is worked out step by step, so you can follow or check the arithmetic.
Temperatures below absolute zero (0 K, −273.15 °C, −459.67 °F) are rejected, because nothing can be colder. A separate temperature difference mode converts changes and gaps — “it got 10 °C warmer” is a rise of 18 °F, not 50 °F — by scaling without the offset.
The arithmetic is exact: 98.6 °F is exactly 37 °C, and results are rounded only when a value would never end (marked ≈).
How to use it
- Choose A temperature for a reading (weather, oven, body, lab) or A temperature difference for a change or gap between two temperatures.
- Type the number in From and pick its scale, then pick the scale you want in To. Negative values are fine — type a minus sign.
- Or type a conversion in Quick convert, such as
37 C to F,-40 F in Cor300 K to C, and press Enter. - Read the result and the Working, step by step panel; copy the result, the working or a link, or download the table of every scale as CSV.
Examples
37 °C to °F
98.6 °F
37 × 1.8 + 32 = 66.6 + 32 = 98.6.
100 °F to °C
≈ 37.77777778 °C
(100 − 32) ÷ 1.8 = 68 ÷ 1.8 = 37.7…
−40 °C to °F
−40 °F
25 °C to K
298.15 K
difference of 10 °C to °F
18 °F (no +32 for differences)
−300 °C
Rejected: the lowest possible temperature is −273.15 °C
Common uses
- Weather forecasts and thermostat settings from abroad.
- Oven temperatures in recipes written in °C or °F.
- Science and engineering work in kelvin and Rankine.
- Converting temperature changes, tolerances and gradients (ΔK, Δ°F) correctly.
- Reading historical texts that use Réaumur, Rømer, Delisle or Newton degrees.
The formulas
From the BIPM SI Brochure (9th edition), NIST Handbook 44 (2026), Appendix C and, for Rankine, NIST SP 811, Appendix B.8:
- Celsius ↔ kelvin: °C = K − 273.15, so K = °C + 273.15. A degree Celsius is the same size as a kelvin.
- Celsius ↔ Fahrenheit: °F = °C × 1.8 + 32 and °C = (°F − 32) ÷ 1.8.
- Fahrenheit ↔ kelvin: K = (°F + 459.67) ÷ 1.8.
- Rankine: an absolute scale with Fahrenheit-sized degrees: °R = K × 1.8 = °F + 459.67.
Any other pair is converted through degrees Celsius, and the working shows both steps.
Historical scales
These scales are converted using the definitions in common use today, fixed by the freezing and boiling points of water (0 °C and 100 °C). Their inventors’ original reference points differed, so very old readings may not match exactly.
- Réaumur (°Ré): water freezes at 0 and boils at 80, so °Ré = °C × 0.8.
- Rømer (°Rø): freezes at 7.5, boils at 60, so °Rø = °C × 21/40 + 7.5.
- Delisle (°De): runs backwards — water boils at 0 and freezes at 150, so °De = (100 − °C) × 1.5.
- Newton (°N): freezes at 0, boils at 33, so °N = °C × 0.33.
Temperatures versus temperature differences
A reading needs the offset (the +32 or +273.15), a difference does not. If water warms from 20 °C to 30 °C, the rise is 10 °C, which is 10 K or 18 °F — not 50 °F, which is what converting “10 °C” as a reading would give. Choose A temperature difference for changes, gaps, tolerances and rates such as “per °C”. In that mode negative values are allowed, and the Delisle scale, which runs backwards, shows a rise as a negative number.
Limitations
- The historical scales use today’s two-fixed-point definitions, not their inventors’ original (and sometimes inconsistent) reference points.
- Reference values such as body temperature and the boiling point of water are typical figures for orientation, not measurements — the boiling point falls with altitude, and normal body temperature varies between people.
- Inputs are limited to 60 characters; very large or very small values are shown in scientific notation.
Privacy
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Frequently asked questions
How do I convert Celsius to Fahrenheit?
Multiply by 1.8 (or 9/5) and add 32: °F = °C × 1.8 + 32. For 25 °C: 25 × 1.8 = 45, and 45 + 32 = 77 °F. The reverse is °C = (°F − 32) ÷ 1.8.
Is 37 °C really 98.6 °F?
Yes, exactly: 37 × 1.8 + 32 = 98.6. The figure is the commonly quoted average body temperature; a normal temperature varies from person to person and through the day.
At what temperature are Celsius and Fahrenheit the same?
At −40: −40 °C = −40 °F. It is the only value where the two scales meet.
Why do kelvin values have no degree sign?
The kelvin is the SI unit of temperature and is written without “degree”: 300 K, not 300 °K. A change of 1 K is the same as a change of 1 °C.
Why does a 10 °C rise convert to 18 °F and not 50 °F?
Because it is a difference. The +32 in the Fahrenheit formula moves the zero point, which matters for readings but cancels out when you subtract two temperatures. Use A temperature difference mode for changes.
Why is −300 °C rejected?
Absolute zero, 0 K = −273.15 °C = −459.67 °F, is the lowest temperature possible, so anything below it is not a real temperature. (In difference mode negative values are fine, because a temperature can fall.)