Kelvin to Celsius Converter

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Enter a Kelvin temperature to find its matching temperature in degrees Celsius, including valid readings below freezing.

Advanced options
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How to use our Kelvin to Celsius Converter

  1. Enter one complete temperature reading in "Temperature in Kelvin (K)," such as 300, 273.15, or 273.15 K.
  2. Open "Advanced options" only if you need decimal or scientific notation for a worksheet, lab record, or technical document.
  3. Select Calculate to see the converted "Temperature in Celsius" value.
  4. Check the answer against a reference point: 273.15 K equals 0 deg C, and a valid value below 273.15 K gives a negative Celsius temperature.
Example inputs for Kelvin to Celsius Converter
Example inputs for Kelvin to Celsius Converter

Definitions

Kelvin (K): The SI base unit for thermodynamic temperature. A complete Kelvin temperature cannot be below 0 K.

Degrees Celsius (deg C): A temperature scale in which 0 deg C is equal to 273.15 K.

Complete temperature reading: A temperature with a defined zero point, such as 300 K. Converting it to Celsius requires the 273.15 offset.

Temperature change: The difference between two temperatures. A change of 1 K is the same size as a change of 1 deg C.

Scientific notation: A compact way to write very large or very small numbers, such as 2.5e-7.

Common mistakes and quick fixes

Mistake: Adding 273.15 to the Kelvin reading.
Fix: Check Temperature in Kelvin (K) and then recalculate. Subtract 273.15 to convert a complete Kelvin temperature to degrees Celsius.

Mistake: Entering a value below 0 K.
Fix: Check Temperature in Kelvin (K) and then recalculate. Enter 0 K or a higher complete temperature reading. Kelvin temperatures cannot be below 0 K.

Mistake: Typing a range such as "273 to 300 K."
Fix: Check Temperature in Kelvin (K) and then recalculate. Enter one temperature at a time, such as 273.15 or 273.15 K.

Mistake: Treating a negative Celsius answer as an error.
Fix: Check Temperature in Kelvin (K) and then recalculate. A negative Celsius value is valid for Kelvin readings from 0 K up to, but not including, 273.15 K.

Mistake: Using a temperature change as though it were a complete temperature.
Fix: Check Temperature in Kelvin (K) and then recalculate. Do not subtract 273.15 from a temperature change. A change of 1 K has the same size as a change of 1 deg C.

Limitations & Key Assumptions / Boundary Conditions

  • This converter is for complete thermodynamic temperature readings in K, not temperature changes.
  • Values below 0 K are rejected because they are outside the thermodynamic Kelvin scale.
  • The calculation uses the exact 273.15-degree offset, but displayed digits cannot make the source measurement more precise.
  • Automatic format uses scientific notation for very large results and nonzero results very close to zero.
  • Input is limited to 15 significant digits because ordinary JavaScript number handling cannot reliably preserve more entered precision.

Methodology

Conversion rule

Subtract 273.15 from a complete Kelvin reading to get degrees Celsius. This relationship follows the defined Kelvin and Celsius temperature scales.

Temperature in Celsius (deg C) = Temperature in Kelvin (K) - 273.15

Worked example

For 300 K, subtract 273.15 from 300. The temperature is 26.85 deg C.

300 K - 273.15 = 26.85 deg C

At the lower valid boundary, 0 K converts to -273.15 deg C. The offset is used only for complete temperature readings; it is not used for a temperature change.