Kelvin converter
K = °C + 273.15
Convert Kelvin, Celsius, and Fahrenheit with absolute-scale formulas and a free live converter.
Kelvin conversion formulas
Kelvin shares the same degree size as Celsius. The only difference is the zero point: 0K is absolute zero, where molecular thermal motion would stop. So conversion is just a shift of 273.15.
Celsius to Kelvin: K = °C + 273.15. Kelvin to Celsius: °C = K − 273.15. Example: room temperature near 25°C is 298.15K.
Fahrenheit to Kelvin: K = (°F − 32) × 5/9 + 273.15. Kelvin to Fahrenheit: °F = (K − 273.15) × 9/5 + 32. Freezing water lands at 32°F = 0°C = 273.15K — the same brand identity as this site.
In SI usage, the unit is written as kelvin (symbol K) without a degree sign. You say “273.15 kelvin,” not “273.15 degrees Kelvin.”
Common Kelvin conversions
Absolute zero, freezing, room temperature, and boiling — mapped across all three scales.
| Kelvin (K) | Celsius (°C) | Fahrenheit (°F) | Notes |
|---|---|---|---|
| 0 | −273.15 | −459.67 | Absolute zero |
| 273.15 | 0 | 32 | Freezing point of water |
| 298.15 | 25 | 77 | Common room temperature |
| 373.15 | 100 | 212 | Boiling point of water |
Absolute zero
Absolute zero (0K) is the lower limit of the thermodynamic temperature scale. It equals −273.15°C and −459.67°F. You can approach it in laboratories, but the third law of thermodynamics says you cannot reach it in a finite number of steps.
Because Kelvin starts at that limit, thermodynamic equations often use K directly. Gas laws, heat engines, and black-body radiation care about absolute temperatures — ratios and products of kelvin values — not about whether water freezes at 0 or 32 on a relative scale.