What is the formula to convert Celsius to Fahrenheit?

Multiply by 9/5 and add 32. The multiplication accounts for Fahrenheit's smaller degree and the addition for its different zero point — both are needed, which is why temperature conversion is not a simple ratio.

At what temperature do Celsius and Fahrenheit agree?

Minus 40. It is the single point where the two scales cross, so −40°C and −40°F are the same temperature — a useful sanity check on any conversion.

Why does Kelvin have no degree symbol?

Because it is an absolute scale, not a relative one. It measures from absolute zero rather than from an arbitrary reference, so a value is simply 300 K rather than 300 degrees Kelvin.

What is absolute zero in Celsius and Fahrenheit?

−273.15°C and −459.67°F. It is the point at which a system has minimum thermal energy, and it cannot be reached — only approached, which laboratories have done to within billionths of a degree.

Is normal body temperature 37°C or 98.6°F?

Both, and the precision of 98.6 is an artefact of conversion. The original 19th-century measurement was 37°C to two significant figures; converting it produced 98.6, which reads as far more precise than the underlying figure ever was.

Temperature Converter

Convert Celsius, Fahrenheit and Kelvin, with the formula shown.

UnitsRuns in your browserFree, no signup

About the Temperature Converter

Convert between Celsius, Fahrenheit and Kelvin in one place. Values update as you type, and the result is calculated by converting to a base unit and back — so the arithmetic is the same in both directions and round-tripping a number returns exactly what you started with.

Temperature is the one conversion that cannot be done by multiplication alone, because the scales do not share a zero. Celsius and Fahrenheit have different zero points and different degree sizes, so the conversion needs both a scale factor and an offset — which is why doubling 20°C does not give you double the temperature in Fahrenheit.

Kelvin shares Celsius's degree size but starts at absolute zero, the point at which molecular motion stops. That is why it has no negative values and no degree symbol: it is an absolute scale, and 0 K is the coldest anything can be rather than an arbitrary reference like the freezing point of water.

How it works

Type a value and choose the units to convert between.
The result updates as you type, with the same value shown in every other unit below.
Jump straight to a direct page for the common conversions listed at the bottom.

Frequently asked questions

What is the formula to convert Celsius to Fahrenheit?: Multiply by 9/5 and add 32. The multiplication accounts for Fahrenheit's smaller degree and the addition for its different zero point — both are needed, which is why temperature conversion is not a simple ratio.
At what temperature do Celsius and Fahrenheit agree?: Minus 40. It is the single point where the two scales cross, so −40°C and −40°F are the same temperature — a useful sanity check on any conversion.
Why does Kelvin have no degree symbol?: Because it is an absolute scale, not a relative one. It measures from absolute zero rather than from an arbitrary reference, so a value is simply 300 K rather than 300 degrees Kelvin.
What is absolute zero in Celsius and Fahrenheit?: −273.15°C and −459.67°F. It is the point at which a system has minimum thermal energy, and it cannot be reached — only approached, which laboratories have done to within billionths of a degree.
Is normal body temperature 37°C or 98.6°F?: Both, and the precision of 98.6 is an artefact of conversion. The original 19th-century measurement was 37°C to two significant figures; converting it produced 98.6, which reads as far more precise than the underlying figure ever was.

Privacy

Everything happens locally. Your files are read by your own browser, processed on your device, and never uploaded — closing the tab is all it takes to erase them.

Related Units tools

Unit Converter

Every measurement in one place — length, weight, temperature, volume, area, speed, data and time.

Length Converter

Convert metres, feet, inches, miles, yards and more — instantly, in your browser.

Weight Converter

Convert kilograms, pounds, ounces, stones and tonnes with one tap.

Volume Converter

Convert litres, gallons, cups, pints, spoons and fluid ounces.