About the Temperature Converter
This temperature converter changes a reading between Fahrenheit, Celsius, Kelvin and Rankine in one step. Pick the scale you are starting from and the scale you want, and it shows the converted value along with the same temperature on every other scale, so you never have to run the formula twice.
It suits cooks following a recipe from another country, travellers checking a weather forecast, students working through physics and chemistry problems in kelvin, and engineers who still meet Rankine in US thermodynamics tables. A chart places your value next to familiar landmarks such as freezing water, room temperature, body temperature and boiling water.
All conversions use the exact definitions (0 °C = 273.15 K = 32 °F, and a Celsius degree is 1.8 Fahrenheit degrees). Values below absolute zero are flagged because they cannot exist physically.
With the default inputs, the converted temperature is 22.22. Change any value above to recalculate instantly.
How to use the temperature converter
- 1Type the temperature you want to convert (negative values are allowed).
- 2Choose the scale it is in under “From”.
- 3Choose the scale you need under “To”.
- 4Read the converted value, and see the other scales and the reference chart below it.
Formula and method
The converter first turns your input into Celsius, then converts from Celsius to every other scale. Fahrenheit and Celsius differ in both size and zero point: a Celsius degree is 1.8 times a Fahrenheit degree and water freezes at 32 °F, hence °F = °C × 1.8 + 32.
Kelvin uses Celsius-sized degrees but starts at absolute zero, so K = °C + 273.15. Rankine is the absolute scale with Fahrenheit-sized degrees: °R = °F + 459.67 = K × 1.8. Because every step is a linear formula, the results are exact apart from display rounding.
- °C
- Degrees Celsius
- °F
- Degrees Fahrenheit
- K
- Kelvin (absolute, SI unit)
- °R
- Degrees Rankine (absolute, Fahrenheit-sized degrees)
Worked examples
72 °F room temperature to Celsius
(72 − 32) × 5/9 = 22.22 °C. Adding 273.15 gives 295.37 K, and 72 + 459.67 = 531.67 °R.
100 °C boiling water to Fahrenheit
100 × 9/5 + 32 = 212 °F. On the absolute scales that is 373.15 K and 671.67 °R.
300 K lab sample to Celsius
300 − 273.15 = 26.85 °C, which is 80.33 °F. Rankine is simply 300 × 1.8 = 540 °R.
The −40 crossover
−40 × 9/5 + 32 = −40, the one temperature where Celsius and Fahrenheit read the same number.
Frequently asked questions
What is the formula to convert Fahrenheit to Celsius?+
Subtract 32 and multiply by 5/9: °C = (°F − 32) × 5/9. For example, 68 °F becomes (68 − 32) × 5/9 = 20 °C.
What is the formula to convert Celsius to Fahrenheit?+
Multiply by 9/5 (1.8) and add 32: °F = °C × 1.8 + 32. So 25 °C × 1.8 + 32 = 77 °F. A rough shortcut is double it and add 30.
At what temperature are Celsius and Fahrenheit equal?+
At −40 degrees. Setting °F = °C in the formula gives x = 1.8x + 32, which solves to x = −40, so −40 °C and −40 °F are the same temperature.
Why is there no degree symbol on kelvin?+
Kelvin is an absolute SI base unit measured from absolute zero, so since 1967 it is written simply as K (e.g. 300 K), not °K.
What is absolute zero?+
Absolute zero is 0 K, equal to −273.15 °C, −459.67 °F and 0 °R. It is the lowest possible temperature, where a system has its minimum thermal energy.
What is normal body temperature in Celsius?+
The traditional figure is 37 °C (98.6 °F), though healthy adults typically range from about 36.1 °C to 37.2 °C depending on time of day and measurement site.