Temperature Conversion Formulas: Celsius, Fahrenheit & Kelvin
Learn how non-linear temperature scales work and master conversions between °C, °F, Kelvin, and Rankine.
Why Temperature Conversions Are Unique
Unlike distance or weight, temperature scales do not share a common zero point (with the exception of thermodynamic absolute zero scales like Kelvin and Rankine). Because of this zero-point offset, temperature conversions require both multiplication and addition/subtraction.
Watch Out for the Zero Offset
You cannot simply multiply Celsius by a constant to get Fahrenheit. You must always account for the 32-degree freezing point offset.
Exact Mathematical Formulas
Mental shortcut: Double the Celsius temperature and add 30 for an easy rough estimate (e.g. 20°C × 2 + 30 ≈ 70°F, exact is 68°F)
Subtract 32 first before multiplying by 5/9
0 Kelvin represents absolute zero, the theoretical cessation of all thermal particle motion
Key Benchmark Reference Points
| State / Phenomenon | Celsius (°C) | Fahrenheit (°F) | Kelvin (K) |
|---|---|---|---|
| Absolute Zero | -273.15 °C | -459.67 °F | 0 K |
| Water Freezing Point | 0 °C | 32 °F | 273.15 K |
| Comfortable Room Temp | 20 to 22 °C | 68 to 72 °F | 293.15 K |
| Normal Human Body Temp | 37 °C | 98.6 °F | 310.15 K |
| Water Boiling Point | 100 °C | 212 °F | 373.15 K |