Skip to content
Utilboxes

Temperature Converter

Convert between Celsius, Fahrenheit, Kelvin and Rankine. All four scales update together as you type.

Runs entirely in your browser

How to use the Temperature Converter

  1. 1Type a temperature into any of the four boxes.
  2. 2The other three update immediately.
  3. 3Use the reference points below for a quick sanity check.

How it works

Temperature is the odd one out among unit conversions, because these scales have different zero points as well as different step sizes. That is why you cannot convert by multiplying alone — you have to shift as well as scale.

Celsius and Kelvin share a step size and differ only in where zero sits: 0 °C is 273.15 K. Fahrenheit uses a step five-ninths the size, with its zero further down again. Rankine is to Fahrenheit what Kelvin is to Celsius — an absolute scale using Fahrenheit-sized degrees.

Absolute zero is the floor: −273.15 °C, −459.67 °F, or 0 K. Values below it are physically impossible, and the tool flags them rather than converting nonsense.

The formula

°F = °C × 9/5 + 32 °C = (°F − 32) × 5/9 K = °C + 273.15 °R = °F + 459.67
°C
degrees Celsius
°F
degrees Fahrenheit
K
kelvin, the absolute scale with Celsius-sized steps
°R
degrees Rankine, absolute with Fahrenheit-sized steps

−40 is the one point where Celsius and Fahrenheit agree, which makes it a handy check.

Worked example

Converting a 180 °C oven temperature

  1. 180 × 9/5 = 324
  2. 324 + 32 = 356

Result: 356 °F, or 453.15 K.

Frequently asked questions

How do I convert Celsius to Fahrenheit in my head?
Double it and add 30 for a rough answer — 20 °C gives about 70 °F, close to the exact 68. For accuracy, multiply by 1.8 and add 32.
What temperature is the same in Celsius and Fahrenheit?
−40. It is the single point where the two scales cross.
Why does Kelvin have no degree symbol?
Kelvin is an absolute unit rather than a scale of degrees, so it is written as 300 K, not 300 °K.
What is absolute zero?
0 K, equal to −273.15 °C or −459.67 °F — the point where thermal motion is at its minimum. Nothing can be colder.

Related tools

Length ConverterMetres, feet, inches, miles and eleven other length units.Weight ConverterKilograms, pounds, stones, ounces and grams.Speed Converterkm/h, mph, knots, m/s and the speed of sound.Volume ConverterLitres, gallons, cups and spoons — US and imperial kept apart.