Converters
Convert temperatures between Celsius, Fahrenheit, and Kelvin.
Enter your numbers to see the answer.
Temperature converter guide
Temperature is the one converter on this site that cannot use a simple multiplier, because Celsius and Fahrenheit place zero in different spots. Water freezes at 0 °C and 32 °F and boils at 100 °C and 212 °F, so a Celsius degree is 9/5 of a Fahrenheit degree and the scales are offset by 32. Kelvin is the SI base unit; it has the same step size as Celsius but starts at absolute zero, so 0 °C is 273.15 K exactly and there are no negative kelvins. The converter takes any value in °C, °F, or K, converts it to Celsius, then to the destination scale, and shows all three side by side. Use it for weather forecasts abroad, oven settings in imported recipes, fever readings, lab work, and datasheets that quote operating ranges in one scale. Both formulas are exact definitions, so the only rounding is the two-decimal display.
°F = °C × 9/5 + 32; °C = (°F − 32) × 5/9; K = °C + 273.15; °C = K − 273.15. Fahrenheit to Kelvin goes through Celsius: K = (°F − 32) × 5/9 + 273.15.
Worked example with the defaults: 20 °C to Fahrenheit. Multiply by 9/5: 20 × 9 ÷ 5 = 36. Add the offset: 36 + 32 = 68 °F, which is the displayed figure. The Kelvin row is 20 + 273.15 = 293.15 K. Reverse it: (68 − 32) × 5 ÷ 9 = 36 × 5 ÷ 9 = 20 °C. A fever reading of 100 °F becomes (100 − 32) × 5 ÷ 9 = 37.78 °C, and a 350 °F oven is (350 − 32) × 5 ÷ 9 = 176.67 °C.
Choose C, F, or K and type the reading as a plain number; negative values are fine for Celsius and Fahrenheit, but Kelvin cannot go below 0. The display uses °C and °F with the degree sign and K without it, following SI style. Rankine (°F + 459.67) is not offered; convert Rankine to Fahrenheit by subtracting 459.67 first. Results round to two decimals, which is finer than any household thermometer.
Unit conversion is exact when the conversion factor is exact, so the only real uncertainty here is rounding and the precision of your input. Where a unit has more than one definition — US versus imperial measures, or short versus metric tons — the wrong variant produces a plausible-looking but wrong answer. The units note above states which definition this page uses. On this page the figure rests entirely on value, from and to, so start there if the temperature converter returns something you did not expect.
Good to know: the offset is the usual slip. Multiplying 20 °C by 1.8 without adding 32 gives 36, not 68. Temperature differences work differently from temperatures: a rise of 10 °C is a rise of 18 °F, with no 32 added, and a change of 1 K equals a change of 1 °C. The mental shortcut “double and add 30” gives 70 °F for 20 °C, 2 degrees high; the error grows to 6 °F at 40 °C. And −40 is the one reading that is identical on both scales.
Conversion results use stated mathematical factors and display precision. For regulated, medical, engineering, or contractual work, confirm the required standard and precision.
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How it works
Convert temperatures between Celsius, Fahrenheit, and Kelvin. This tool explains the calculation so you can adjust the assumptions to match your situation.
Worked example
With Value = 20 · From = C · To = F → 68 °F (20 °C converted to °F). Change an input above and this example updates with your numbers.
Common questions
20 °C is 68 °F: 20 × 9 ÷ 5 = 36, plus 32. That is a mild spring day. For comparison 25 °C is 77 °F, 30 °C is 86 °F, and 37 °C, normal body temperature, is 98.6 °F.
Subtract 32, then multiply by 5/9. For 100 °F: (100 − 32) × 5 ÷ 9 = 37.78 °C. For a quick estimate, subtract 30 and halve: 100 °F → 35 °C, about 3 degrees low; the exact rule is always available here.
350 °F is 176.67 °C, so set a Celsius oven to 175–180 °C. The common oven marks convert as 325 °F = 163 °C, 375 °F = 191 °C, 400 °F = 204 °C, and 450 °F = 232 °C. Fan ovens usually run about 20 °C cooler than the dial.
Add 273.15. Room temperature of 20 °C is 293.15 K, and 25 °C, the usual reference for datasheets, is 298.15 K. Kelvin has no degree sign and no negative values; absolute zero, 0 K, is −273.15 °C or −459.67 °F.
At −40. Setting °C = °F in the formula gives x = 1.8x + 32, so x = −40. Below that Fahrenheit readings are lower than Celsius, above it they are higher, and the gap is 32 at 0 °C.