Temperature converter

Temperature conversion formulas

To convert Celsius to Fahrenheit, multiply by 9/5 and add 32. To convert Fahrenheit to Celsius, subtract 32 and multiply by 5/9. Kelvin has the same interval size as Celsius but begins at absolute zero. Because Celsius and Fahrenheit have different zero points, temperature conversion is not a simple one-factor multiplication.

Worked conversion examples

For 20°C, multiplying by 9/5 gives 36 and adding 32 produces 68°F. For 95°F, subtracting 32 gives 63 and multiplying by 5/9 produces 35°C. Converting 20°C to kelvin adds 273.15, producing 293.15 K.

Reference points and a useful cross-check

At standard atmospheric pressure, water freezes near 0°C or 32°F and boils near 100°C or 212°F. These points change with pressure and water purity. A useful mathematical cross-check is −40°, where Celsius and Fahrenheit have the same numeric value.

Kelvin and absolute zero

Zero kelvin equals −273.15°C and represents absolute zero. Scientific style writes kelvin without a degree symbol. Negative kelvin values are not valid on the ordinary thermodynamic scale, so the calculator reports an error when a conversion would begin below absolute zero.

Absolute temperatures versus differences

A temperature change of 1 kelvin equals a change of 1 Celsius degree, while a Fahrenheit degree is 5/9 as large. However, an absolute reading of 1 K is not 1°C because the scales have different origins. This distinction matters when converting temperature differences in engineering formulas.

Displayed results are rounded for readability. Physical readings include instrument uncertainty, and familiar water reference points depend on pressure and purity. Use calibrated instruments and appropriate uncertainty rules for scientific, medical, food-safety, or other safety-critical work.