The method
Temperature conversion formulas
Temperature scales use different starting points and intervals. Celsius and Kelvin use the same interval size; Fahrenheit divides the distance between water’s freezing and boiling points into 180 degrees.
°F = (°C × 9/5) + 32Example: (25 × 9/5) + 32 = 77°F°C = (°F − 32) × 5/9Example: (77 − 32) × 5/9 = 25°CK = °C + 273.15Example: 25 + 273.15 = 298.15 KVerify the calculation
Formula
Conversions use exact scale relationships: °F = (°C × 9/5) + 32 and K = °C + 273.15.
Example
25°C converts to (25 × 9/5) + 32 = 77°F.
Methodology
Values retain full precision internally. The decimal-place control changes presentation only. Read our methodology.
Sources
Temperature reference table
| Celsius | Fahrenheit | Kelvin | Reference |
|---|---|---|---|
| −40°C | −40°F | 233.15 K | Scales meet |
| 0°C | 32°F | 273.15 K | Water freezes |
| 20°C | 68°F | 293.15 K | Room temperature |
| 37°C | 98.6°F | 310.15 K | Body temperature |
| 100°C | 212°F | 373.15 K | Water boils* |
*At standard atmospheric pressure.
Frequently asked questions
What is the fastest way to estimate Celsius to Fahrenheit?
Double the Celsius value and add 30 for a quick estimate. For an accurate result, multiply by 9/5 and add 32.
Why does Kelvin not use a degree symbol?
Kelvin is an absolute thermodynamic scale. Its unit is written as K, not °K.
Can temperature be below absolute zero?
On the ordinary thermodynamic scale, 0 K (−273.15°C) is absolute zero and lower values are not physically defined.