Celsius to Kelvin Converter

Kelvin and Celsius use the same size degree, so the conversion is addition alone:

K = °C + 273.15

That shared step size is deliberate. The kelvin was defined so that a one-degree change means the same thing on both scales; only the zero point differs. Which means a temperature difference of 10°C is a difference of 10 K exactly — no conversion needed.

Kelvin has no degree symbol and no "degrees". It is written 300 K, not 300°K, and read as "300 kelvin". Celsius and Fahrenheit take the degree sign because they are relative scales; kelvin is absolute.

Zero kelvin is absolute zero — −273.15°C — the point at which a system has no thermal energy left to remove. It is unreachable in principle, not merely in practice: the third law of thermodynamics rules it out in any finite number of steps. Laboratories have reached within a few billionths of a kelvin.

Reference points:

• 0 K → −273.15°C — absolute zero
• 77 K → −196.15°C — liquid nitrogen, the everyday laboratory cold
• 273.15 K → 0°C — water freezes
• 293.15 K → 20°C — "room temperature" in most physics problems
• 310.15 K → 37°C — body temperature
• 373.15 K → 100°C — water boils at sea level

Why it matters outside a lab: the gas laws, thermal radiation, and anything involving a ratio of temperatures only work in absolute units. Doubling the pressure of a gas at constant volume doubles its kelvin temperature — a calculation that is meaningless in Celsius, where the zero is arbitrary.

To convert back, subtract 273.15.