Celsius to Kelvin
Convert Celsius to Kelvin instantly. Free temperature converter, no signup.
How to use this tool
- Enter degrees celsius in the fields above.
- Results update instantly as you type — or click Calculate.
- Read your degrees kelvin and the full breakdown beneath it.
Convert Celsius to Kelvin instantly. Free temperature converter, no signup.
Formula
Kelvin = Celsius + 273.15
K = °C + 273.15
The offset 273.15 is the absolute zero point expressed in Celsius — the temperature at which all thermal motion theoretically stops.
How it works
Add 273.15 to the Celsius value. The Kelvin scale shares the same degree size as Celsius but starts at absolute zero (0 K = −273.15 °C), so the conversion is purely a shift — no multiplication needed. Kelvin is the SI base unit for thermodynamic temperature and is used in scientific equations such as the ideal gas law.
Common mistake: Some people subtract 273.15 instead of adding it — this produces the inverse conversion (Kelvin to Celsius). Always add when going from Celsius to Kelvin.
Worked example
Convert 0 °C (the freezing point of water) to Kelvin
- Start with 0 °C (the input value).
- Apply the formula: K = 0 + 273.15
- Result: 273.15 K
273.15 K — the freezing point of water on the Kelvin scale.
Common mistakes to avoid
- Adding 273 instead of 273.15, introducing a 0.15 K error that matters in thermodynamic calculations.
- Confusing the direction and subtracting 273.15 (the Kelvin-to-Celsius formula) instead of adding.
- Entering a negative Celsius value and expecting a negative Kelvin result — Kelvin cannot be negative; -273.15 C is the minimum (0 K).
Key terms
- Kelvin (K)
- The SI base unit of thermodynamic temperature. Zero Kelvin is absolute zero; degree size is identical to one Celsius degree.
- Absolute zero
- The lowest theoretically possible temperature, 0 K = −273.15 °C, where particles have minimum thermal energy.
- Celsius (°C)
- A temperature scale where water freezes at 0 °C and boils at 100 °C under standard atmospheric pressure.
- Offset conversion
- A conversion that shifts a value by a fixed constant rather than scaling it — adding or subtracting rather than multiplying.
Frequently asked questions
- What is 0 C in Kelvin?
- 0 C + 273.15 = 273.15 K, the freezing point of water on the absolute scale.
- Can Kelvin be negative?
- No. 0 K (absolute zero, -273.15 C) is the lowest possible temperature; negative Kelvin values are physically undefined in classical thermodynamics.
- Why is the offset 273.15 and not 273?
- 273.15 is the experimentally determined absolute zero expressed in Celsius. Using 273 introduces a 0.15 K rounding error that matters in precise scientific work.