Celsius to Kelvin

What the Celsius to Kelvin does

Celsius to Kelvin: converts Celsius to Kelvin through temperature's base unit, so the result is exact rather than rounded. Example: 25 °C = 298.15 K.

Point it at Temperature, From and To and it returns Result, How it was calculated and Reverse conversion. Results refresh instantly, so trying variations costs nothing but a moment.

Two industries often use the same word for slightly different quantities. That is usually what brings people following a recipe or spec written elsewhere here.

This runs client-side, which means we never receive what you enter and could not retrieve it if asked.

The sections that follow cover the fields, the method, and one full example computed from the defaults.

What do the Celsius to Kelvin fields mean?

The Celsius to Kelvin uses 3 inputs. Every field is populated on load; treat those numbers as a template rather than a suggestion.

How does the Celsius to Kelvin work?

Temperature scales differ in where zero sits as well as in step size, so this is an offset plus a scale, not a single multiplying factor. That is why you cannot convert a temperature *difference* with the same expression you use for a temperature.

Definitions are taken from the SI system where one exists, and from CODATA or the IAU where a unit is established by measurement. No factor is rounded before the calculation.

Worked example

These are the values the Celsius to Kelvin loads by default, and the result it produces from them. This walkthrough uses the starting values, which means you can follow along without typing anything.

Celsius and Kelvin

Kelvin and Celsius use the same size degree, so converting between them is pure addition: K = °C + 273.15, with no multiplication involved at all, the only conversion on this page that’s simpler than a ratio.

Worth knowing

• Kelvin is an absolute scale: 0 K is absolute zero, the coldest temperature theoretically possible, equal to exactly −273.15°C. Nothing can go below it, which is why Kelvin (not Celsius) is the scale physics and chemistry formulas actually require (gas laws, blackbody radiation, thermodynamic equations all assume a true zero point).
• Kelvin values are never written with a degree symbol (it’s "300 K," not "300°K") a small but real convention formalised in 1967 when Kelvin was redefined from "degrees Kelvin" to simply "kelvin."
• Room temperature is roughly 293 to 298 K (20 to 25°C); the coldest recorded natural temperature on Earth’s surface, at Vostok Station in Antarctica, was about 184 K (−89.2°C), still nowhere near absolute zero.

Definitions: BIPM SI Brochure · NIST reference on units

How to use it

1. Enter Temperature.
2. Pick a value for From: the options are Celsius (°C), Fahrenheit (°F), Kelvin (K), Rankine (°R), Réaumur (°Ré) or Delisle (°De).
3. Pick a value for To: the options are Celsius (°C), Fahrenheit (°F), Kelvin (K), Rankine (°R), Réaumur (°Ré) or Delisle (°De).
4. Because it recalculates as you type, you can dial a value in rather than guessing and re-running.
5. You get Result, How it was calculated and Reverse conversion back.
6. Share the link rather than a screenshot. It carries the values with it.

What this tool does not do

• Repeated conversions compound rounding, so convert once from the original value where you can.
• Conversion factors use SI definitions; some industries use their own rounded factors.
• It assumes the values you give are already consistent with each other.
• Results are only as good as the inputs. Check your units before reading anything into the output.

Frequently asked questions

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