Convert Fahrenheit to Celsius

Fahrenheit to Celsius with the working shown

Type a temperature in degrees Fahrenheit and the converter shows the Celsius value, the formula with your number filled in – (98.6 − 32) ÷ 1.8 = 37 – and the same temperature in Kelvin. Negative temperatures and decimals work as well. Use the swap button for Celsius to Fahrenheit.

Unlike length or weight, temperature conversion is not just a multiplication, because the two scales have different zero points. That is why a fixed 'factor' never works and why the formula below has two steps.

The formula

°C = (°F − 32) × 5/9, or (°F − 32) ÷ 1.8

°F = °C × 9/5 + 32

K = °C + 273.15

Example: 72 °F − 32 = 40; 40 ÷ 1.8 = 22.2 °C.

Worked examples

• 32 °F = 0 °C – water freezes.
• 212 °F = 100 °C – water boils at sea level.
• 98.6 °F = 37 °C – normal body temperature.
• 100.4 °F = 38 °C – the usual threshold for a fever.
• 70 °F = 21.1 °C – room temperature.
• 350 °F = 176.7 °C – the most common baking temperature (recipes use 175 or 180 °C).
• −40 °F = −40 °C – the one point where both scales agree.

Quick mental shortcut

Subtract 30 and halve: 80 °F → 50 → 25 °C (exact 26.7 °C). It is within about 2 °C between 40 and 90 °F, which is fine for weather. For cooking and medicine use the exact value.

Fahrenheit to Celsius chart

Oven temperatures

Fan (convection) ovens are usually set about 20 °C lower than conventional ones.

Body temperature and fever

Normal body temperature varies between people and through the day; these values are general guidance, not medical advice.

Weather in Fahrenheit

The United States and a few other countries report weather in Fahrenheit. Useful anchors: 0 °F = −17.8 °C (very cold), 32 °F = 0 °C (freezing), 50 °F = 10 °C (cool), 68 °F = 20 °C (mild), 77 °F = 25 °C (warm), 86 °F = 30 °C (hot), 100 °F = 37.8 °C (heatwave). Each 1 °F change equals 0.56 °C, and each 1 °C change equals 1.8 °F – which matters when converting temperature differences, where the 32 offset does not apply.

Who invented Fahrenheit and Celsius?

Daniel Gabriel Fahrenheit, a German-Dutch instrument maker, proposed his scale in 1724, setting 0 °F at the temperature of a brine mixture and about 96 °F at human body temperature; water's freezing and boiling points ended up at 32 and 212. Anders Celsius, a Swedish astronomer, proposed a 100-degree scale in 1742 based on water's freezing and boiling points (originally inverted, with 0 for boiling). Today the Celsius scale is defined through the Kelvin, the SI unit of temperature, and almost every country uses it for weather.

Why the shortcut fails for big numbers

The 'subtract 30 and halve' trick ignores the exact factor of 1.8 and uses 30 instead of 32. At 50 °F it gives 10 °C – exactly right. At 100 °F it gives 35 °C, while the real answer is 37.8 °C. At 400 °F (oven temperatures) it gives 185 °C instead of 204 °C, an error that matters for baking. For anything above about 100 °F, use the converter or the exact formula.

Cooking and food-safety temperatures

Food-safety values follow common US guidance; check local guidelines for your country.

Temperature differences versus temperatures

If a recipe says 'reduce the oven by 25 °F', that is a change of 25 × 5/9 = 13.9 °C – you do not subtract 32, because the offset cancels out when you take a difference. The same applies to weather reports ('5 °F warmer than yesterday' = 2.8 °C warmer) and to scientific work. The converter converts absolute temperatures; for differences, multiply °F by 0.5556 or °C by 1.8.

Fahrenheit, Celsius and Kelvin together

Scientists use the Kelvin scale, which starts at absolute zero (−273.15 °C, −459.67 °F) and has the same step size as Celsius. Kelvin is written without a degree sign: 300 K = 26.85 °C = 80.33 °F. Rankine is the Fahrenheit equivalent of Kelvin, used occasionally in US engineering: 0 °R is absolute zero and 491.67 °R is the freezing point of water. The converter's temperature category includes °C, °F and K.

Converting in a spreadsheet

In Excel or Google Sheets, put the Fahrenheit value in A2 and use =(A2-32)*5/9 for Celsius, or =CONVERT(A2,"F","C"). For the reverse use =A2*9/5+32 or =CONVERT(A2,"C","F"). Format the cells to one decimal place for weather data. The converter's TXT download lists your value in °C, °F and K, ready to paste into a sheet.

Converting a whole list

Paste a column of Fahrenheit readings into a spreadsheet and apply the formula once, or convert values one at a time here and use the download button to keep a record of each result together with its Kelvin equivalent.

Privacy

The converter runs entirely in your browser. Nothing you type is sent to a server, your values are not tracked, and once the page has loaded it keeps working offline – useful in a workshop, a kitchen, a gym or on a plane.

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