What is kelvin?

Kelvin is the SI base unit of thermodynamic temperature, with its zero point at absolute zero. It is the standard in scientific and engineering fields where absolute temperature values are required, such as thermodynamics and astrophysics.

Real-world uses

Kelvin is the SI base unit for thermodynamic temperature, used in physics, chemistry, and engineering. Colour temperature of lighting (e.g., 5000 K daylight, 2700 K warm white) is specified in kelvins. Cryogenics and astrophysics rely on kelvin exclusively.

History

Named after William Thomson, 1st Baron Kelvin, who proposed an absolute temperature scale in 1848. The scale's zero point represents absolute zero, where molecular motion reaches its minimum. It became an SI base unit in 1954.

Common mistakes

Writing "degrees Kelvin" or "°K"—kelvin uses no degree symbol and is written simply as "K." Also, confusing kelvin with Celsius: 0 K is absolute zero (−273.15°C), not the freezing point of water.

What is degree Celsius?

Degree Celsius is a temperature unit based on the freezing and boiling points of water at standard atmospheric pressure. It is the most widely used scale for weather forecasting, cooking, and everyday temperature reporting worldwide.

Real-world uses

Celsius is used for everyday temperature in most of the world—weather forecasts, cooking temperatures, body temperature (37°C normal), and industrial process controls. Scientific publications outside the US typically report temperatures in °C.

History

Proposed by Swedish astronomer Anders Celsius in 1742, originally with 0° as the boiling point and 100° as freezing. Carl Linnaeus inverted the scale to its modern form shortly after. It was renamed from "centigrade" to "Celsius" in 1948 by the CGPM.

Common mistakes

Assuming Celsius and Fahrenheit scales cross at intuitive points. They intersect at −40°, not at 0° or 100°. Also, confusing a "degree Celsius change" with a "degree Fahrenheit change"—a 1°C change equals a 1.8°F change.

When is this conversion used?

This is the most common temperature conversion worldwide, needed for weather reports, cooking temperatures, and medical readings. Most of the world uses Celsius while the US primarily uses Fahrenheit.

Worked examples

1 kelvin = -272.15 degree Celsius

1 degree Celsius = 1 kelvin

How to convert kelvin to degree Celsius

Temperature conversion uses a formula rather than a constant multiplier. The interactive converter above handles all calculations automatically.

Measurement standards

The kelvin is the SI base unit of thermodynamic temperature, defined by fixing the Boltzmann constant to exactly 1.380649 × 10⁻²³ joules per kelvin. This definition, adopted in 2019, decoupled the kelvin from the triple point of water.

Did you know?

The coldest temperature ever recorded on Earth was −89.2 °C (−128.6 °F) at the Soviet Vostok Station in Antarctica on 21 July 1983. In laboratories, scientists have cooled atoms to within billionths of a kelvin above absolute zero.

Quick reference: kelvin to degree Celsius

Common values

Available Temperature units

• degree Celsius conversions
• degree Fahrenheit conversions
• kelvin conversions
• degree Rankine conversions
• degree Réaumur conversions

More kelvin conversions

• Convert kelvin to degree Celsius
• Convert kelvin to degree Fahrenheit
• Convert kelvin to degree Rankine
• Convert kelvin to degree Réaumur

Assumption: formula-based scales using Kelvin as reference.