Convert Kelvin to Celsius and Celsius to Kelvin. Visual dual scale, step-by-step conversion work, absolute zero validation, and reference temperature table.
The relationship between Kelvin and Celsius is one of the simplest in all of science: subtract 273.15 from Kelvin to get Celsius, or add 273.15 to Celsius to get Kelvin. Both scales use the same degree size — a 1 K change equals a 1 °C change. The only difference is the zero point: Kelvin starts at absolute zero (−273.15 °C), while Celsius starts at water's freezing point.
This converter provides instant bidirectional conversion between Kelvin and Celsius, with Fahrenheit and Rankine shown for completeness. The step-by-step conversion work shows exactly how the result is calculated. The visual dual scale helps you build intuition for the 273.15 offset, and the reference table maps important temperatures in both scales.
This is the go-to conversion for students, scientists, and engineers who work with data in both scales. Lab instruments often report in Celsius, while thermodynamic equations require Kelvin. Quickly verifying the conversion ensures accuracy in calculations where temperature matters.
K ↔ C is the most common scientific temperature conversion. While the math is simple (±273.15), this tool provides instant verification, shows the work, validates against absolute zero, and includes a reference table. It prevents the simple but costly error of adding instead of subtracting. Keep these notes focused on your operational context.
Kelvin to Celsius: °C = K − 273.15 Celsius to Kelvin: K = °C + 273.15 Note: ΔK = Δ°C (same degree size)
Result: 100 °C (boiling point of water)
373.15 K − 273.15 = 100 °C exactly. This is the boiling point of water at standard atmospheric pressure (1 atm). The offset 273.15 is the absolute value of the Celsius temperature of absolute zero.
Celsius was designed for practical everyday use with water's phase transitions as anchors. Kelvin was designed for theoretical physics, where an absolute zero point simplifies the ideal gas law (PV=nRT), entropy calculations, and radiation laws (Wien's law, Stefan-Boltzmann law). Having the same degree size links practical measurement to theoretical physics seamlessly.
For most purposes, K = °C + 273 is accurate enough. The 0.15 matters in precision chemistry, calorimetry, and when using the triple point of water (273.16 K = 0.01 °C) as a calibration standard. Modern temperature measurement can achieve millikelvin precision, making the full 273.15 offset essential.
The most frequent error is confusing temperature differences with absolute temperatures. A 10°C rise = a 10 K rise (same difference). But 10°C ≠ 10 K as absolute temperatures (10°C = 283.15 K). Always clarify whether you mean an absolute temperature or a change in temperature.
Subtract 273.15. Formula: °C = K − 273.15. Example: 300 K − 273.15 = 26.85 °C.
Add 273.15. Formula: K = °C + 273.15. Example: 25 °C + 273.15 = 298.15 K.
Absolute zero was empirically determined to be −273.15 °C based on the ideal gas law extrapolation. The 2019 SI redefinition fixed the Boltzmann constant, which precisely determines this value.
Yes, exactly. A change of 1 K equals a change of 1 °C. Only the zero point differs. This is why the conversion is just an offset (±273.15) rather than a multiplication.
Use Kelvin for: thermodynamic equations (PV=nRT), statistical mechanics, absolute temperature ratios, and any calculation where negative temperatures would be problematic. Use Celsius for everyday weather, cooking, and most lab work.
0 K = −273.15 °C. This is absolute zero — the lowest possible temperature. At this point, atoms have minimum energy. It has never been achieved in practice.