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Temperature Converter: Celsius, Fahrenheit and Kelvin

Converts a temperature between Celsius, Fahrenheit and Kelvin, and also returns the value in Celsius. Enter 100 with C to F to get 212 F.

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Temperature

Example: 100

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Result

Currency

Figures are computed on your device; nothing is sent anywhere.

Formula

celsius = value from C; (value - 32) * 5 / 9 from F; value - 273.15 from K; converted = celsius to C; celsius * 9 / 5 + 32 to F; celsius + 273.15 to K; throw if celsius < -273.15

How the calculation works

Enter the temperature as a number, then choose the scale you are converting from and the scale you want back, for example 100 with C as the from unit and F as the to unit.

The function normalises your value to Celsius first, turning Fahrenheit into (F - 32) * 5 / 9 and Kelvin into K - 273.15, so every conversion passes through one base scale.

It then converts that Celsius value into the target scale, giving 212 F for 100 C, and returns both converted and celsius so you can check the intermediate step.

Common mistakes

Forgetting that Kelvin never goes negative: a value such as -5 K is physically impossible, so the function throws an error when the Celsius result falls below -273.15.
Swapping the scales: 100 C to F is 212 F, but 100 F to C is about 37.78 C, so the two directions give very different numbers.
Adding 32 before scaling when going to Fahrenheit: the correct order is C * 9 / 5 plus 32, and reversing them gives 273.8 instead of 212 for boiling water.

When to use it

Use it when a weather app, oven dial, or science worksheet gives a temperature in Fahrenheit or Kelvin and you need the Celsius figure for a recipe, lab note, or thermostat.
Use it to sanity-check limits: convert a Kelvin reading into Celsius to confirm it sits above absolute zero before you trust a sensor or physics calculation.

Worked example

100 C to F gives converted 212 and celsius 100.

Converted ৳100.00

Temperature in Celsius 100.00

Common questions

What is 100 C in Fahrenheit?

100 C is exactly 212 F, because 100 * 9 / 5 is 180 and adding 32 gives 212, the boiling point of water at sea level.

Why does the function throw an error for very low values?

Nothing can be colder than absolute zero, so if the Celsius result falls below -273.15 the input is impossible and the function throws a CalcError instead of returning a meaningless number.

Last updated: 2026-10-03