Celsius to Kelvin Calculator – Convert °C to K and Vice Versa

Temperature Converter

Temperature in Celsius (°C)

The Celsius to Kelvin Calculator converts temperatures between Celsius (°C) and Kelvin (K), the SI base unit of temperature. Kelvin is an absolute scale starting at absolute zero (-273.15°C), making it essential for scientific calculations like the ideal gas law, thermodynamics, and astronomy. This calculator provides step‑by‑step explanations, making it ideal for students, scientists, and anyone working with temperature conversions in science and engineering.

Celsius to Kelvin Formula

Formula: K = °C + 273.15

Example: 0°C → 0 + 273.15 = 273.15 K

Example: 100°C → 100 + 273.15 = 373.15 K

How to Convert Celsius to Kelvin (Step‑by‑Step)

Start with the temperature in Celsius (°C).
Add 273.15 to the value.
The result is the temperature in Kelvin (K).

Example: 25°C → 25 + 273.15 = 298.15 K

Reverse Conversion – Kelvin to Celsius

Formula: °C = K - 273.15

Example: 273.15 K → 273.15 - 273.15 = 0°C

Example: 373.15 K → 373.15 - 273.15 = 100°C

Common Temperature Reference Points

Description	°C	K
Absolute zero	-273.15	0
Water freezes	0	273.15
Room temperature	20-22	293.15-295.15
Body temperature	37	310.15
Water boils	100	373.15

Real‑World Applications of Kelvin

Physics & chemistry: Ideal gas law (PV = nRT) requires Kelvin to avoid negative temperatures.
Astronomy: Stellar temperatures (e.g., Sun's surface ~5778 K).
Engineering: Thermodynamics, heat engines, and cryogenics.
Meteorology: Some scientific weather models use Kelvin.

What is Absolute Zero?

Absolute zero (0 K) is the lowest possible temperature where all molecular motion stops. It is equivalent to -273.15°C. Kelvin was developed by Lord Kelvin (William Thomson) in 1848 as an absolute scale. Unlike Celsius, Kelvin does not use the degree symbol – it is simply "K".

Common Mistakes When Converting Celsius to Kelvin

Forgetting to add 273.15: Some mistakenly add 273 instead, which introduces a small error for precise work.
Using the degree symbol: Kelvin is written as "K", not "°K" (the degree symbol is not used).
Subtracting instead of adding: The correct direction is °C + 273.15 = K.

Why Kelvin is the Scientific Standard

Kelvin is an absolute scale, meaning 0 K represents the complete absence of thermal energy. Many physical laws (e.g., Charles's law, Gay‑Lussac's law) become simpler and more intuitive when using Kelvin because they involve direct proportionality with temperature. For example, doubling the Kelvin temperature doubles the pressure (at constant volume), but doubling Celsius does not.

Use this celsius to kelvin calculator for science homework, lab work, or any situation requiring accurate temperature conversion. The step‑by‑step output ensures you understand the simple addition/subtraction involved.

Step‑by‑Step Manual Example

Convert 25°C to Kelvin: 25 + 273.15 = 298.15 K

Convert 400 K to Celsius: 400 - 273.15 = 126.85°C

Frequently Asked Questions about Celsius to Kelvin

What is Kelvin?

Kelvin is the SI base unit of temperature. It is an absolute scale where 0 K is absolute zero – the lowest possible temperature. Unlike Celsius, Kelvin does not use the degree symbol (°).

What is the formula for Celsius to Kelvin?

K = °C + 273.15. For example, 0°C = 273.15 K, 100°C = 373.15 K.

What is the formula for Kelvin to Celsius?

°C = K - 273.15. For example, 273.15 K = 0°C, 373.15 K = 100°C.

Why do we use Kelvin in science?

Kelvin starts at absolute zero, making it convenient for scientific calculations (e.g., gas laws, thermodynamics) where proportional relationships hold true.