Explanation
Three scales, different zero points
Celsius, Fahrenheit and Kelvin place zero in different places, so converting a reading needs an offset as well as a factor. Kelvin starts at absolute zero, the coldest possible temperature.
F = C × 9/5 + 32 and K = C + 273.15
| C | reading in degrees Celsius |
|---|---|
| F | reading in degrees Fahrenheit |
| K | reading in kelvin |
0 °C to Fahrenheit
| Value | 0 |
|---|---|
| From | Celsius (°C) |
| To | Fahrenheit (°F) |
| Result | 32 °F |
0 °C = 32 °F
100 °C to kelvin
| Value | 100 |
|---|---|
| From | Celsius (°C) |
| To | Kelvin (K) |
| Result | 373.15 K |
100 °C = 373.15 K
−459.67 °F to kelvin
| Value | -459.67 |
|---|---|
| From | Fahrenheit (°F) |
| To | Kelvin (K) |
| Result | 0 K |
-459.67 °F = 0 K
Diagram of this result
Both scales are drawn over the same range of temperatures. Ticks line up at −40, where Celsius and Fahrenheit agree, at water's freezing point, at body temperature and at water's boiling point; the marker shows the entered reading.
The answer and the steps state both readings with their unit symbols.
Definitions and limits
Absolute zero is exactly 0 K, −273.15 °C and −459.67 °F; readings below it are rejected. Water freezes at 0 °C (32 °F) and boils at 100 °C (212 °F) at sea level. Answers are shown to six significant figures; the calculation keeps every digit.
Common mistakes
A temperature difference converts without the offset: a rise of 10 °C is a rise of 18 °F, not 50 °F. This calculator converts readings. Kelvin is written without a degree sign.
Where do Celsius and Fahrenheit meet?
At −40: −40 °C is exactly −40 °F. Room temperature of 20 °C is 68 °F, and a body temperature of 37 °C is 98.6 °F.
References
NIST SP 811, Guide for the Use of the International System of Units, including its conversion factors: https://www.nist.gov/pml/special-publication-811.