Free Fahrenheit to Celsius Converter

What is a degree Fahrenheit? What is a degree Celsius?

The degree Fahrenheit (°F) is the everyday temperature unit in the United States. Daniel Gabriel Fahrenheit, a Polish-Dutch instrument maker, set it out in the early 1700s, building some of the first reliable mercury thermometers. He put zero at the coldest temperature he could make in his laboratory, with a mixture of ice, water, and salt, and he first put body temperature near 96. The scale was later tidied so that water freezes at exactly 32 °F and boils at exactly 212 °F — a span of 180 degrees. Because the zero point sits well below freezing, everyday US weather rarely needs a minus sign, which is one reason Americans kept the scale.

The degree Celsius (°C) is the everyday temperature unit across Europe and almost everywhere else. Anders Celsius set it out in 1742, built around water: 0 °C is the freezing point and 100 °C is the boiling point at standard atmospheric pressure. That 100-degree span makes Celsius easy to picture — 20 °C is a comfortable room and 30 °C is a hot day. Today the scale is formally defined through the kelvin: 0 °C equals exactly 273.15 K.

One Celsius degree is a bigger step than one Fahrenheit degree: the same change in temperature that measures 100 Celsius degrees measures 180 Fahrenheit degrees, so 1 °C equals a step of 1.8 °F. That is why converting needs both a multiplication and a shift of 32 — the scales differ in step size and in where they put zero.

How to use

1. Type a temperature in Fahrenheit in the left box — the Celsius value appears instantly on the right, with no button to press.
2. Or type in the Celsius box instead: both boxes are editable, and typing in either one updates the other at once.
3. Press Swap to flip the direction. The converted value carries over as the new starting number, so you can keep converting back and forth.
4. Negative numbers work normally — type 0 for a very cold US winter day and you will get −17.7778 °C. The reference table below covers freezing, fever, cooking, and thermostat settings.

Fahrenheit to Celsius formula

To go from Fahrenheit to Celsius, undo the 32 offset first, then scale down by 5/9:

°C = (°F − 32) × 5 ÷ 9

And the reverse direction scales up first, then adds the offset:

°F = (°C × 9 ÷ 5) + 32

• °F — temperature in degrees Fahrenheit
• °C — temperature in degrees Celsius
• 32 — the offset: water freezes at 32 °F but at 0 °C, so it must be removed before scaling
• 5 ÷ 9 (0.5556) — the ratio of the size of one Fahrenheit degree to one Celsius degree

A quick mental check: subtract 30 and halve the result. For 80 °F that gives 25 °C, close to the exact 26.6667 °C — good enough for weather, though you should use the converter for medicine and precise baking. If you need other units in one place, the general unit converter covers more units than any single page here.

Worked example

Fahrenheit to Celsius conversion table

Every value is computed from the exact formula °C = (°F − 32) × 5 ÷ 9. Note how minus 40 is the same on both scales.

Reference points: US weather, fever, and cooking

These are the numbers worth memorising, so a US forecast, thermometer, or recipe makes sense at a glance:

• US weather — 32 °F (0 °C) is freezing; 50 °F (10 °C) is jacket weather; 68–72 °F (20–22.2222 °C) is indoor comfort; 80 °F (26.6667 °C) is warm; 90 °F (32.2222 °C) is hot; 95 °F (35 °C) is a heatwave day.
• Thermostat settings — 68 °F is 20 °C and 72 °F is 22.2222 °C, the usual range for a comfortable home. A heated pool is often kept near 78 °F (25.5556 °C).
• Fever — normal body temperature is 98.6 °F (37 °C); 100.4 °F (38 °C) is generally treated as a fever; 103 °F (39.4444 °C) is a high fever, so follow local health guidance.
• Cooking — a slow oven at 325 °F is 162.7778 °C; the standard baking temperature of 350 °F is 176.6667 °C; a hot oven at 400 °F is 204.4444 °C; roasting at 450 °F is 232.2222 °C.
• Cold snaps — 0 °F is −17.7778 °C, a very cold day anywhere; −40 °F is −40 °C, where both scales agree.

For the background on why Europe and the US ended up with different systems, read the metric vs imperial conversion guide for Europe.

Frequently asked questions

How do I convert Fahrenheit to Celsius?

Subtract 32 from the Fahrenheit temperature, then multiply by 5 and divide by 9. For example, 72 minus 32 is 40, times 5 divided by 9 is 22.2222 degrees Celsius.

What is 72 degrees Fahrenheit in Celsius?

72 degrees Fahrenheit is 22.2222 degrees Celsius. Seventy-two Fahrenheit is a common indoor thermostat setting in the US, and 22 degrees is the comfortable room temperature Europeans expect.

What is 98.6 degrees Fahrenheit in Celsius?

98.6 degrees Fahrenheit is 37 degrees Celsius, the standard figure for normal body temperature. A thermometer reading of 100.4 Fahrenheit equals 38 Celsius, which is generally treated as a fever.

What Fahrenheit temperature is freezing?

Water freezes at 32 degrees Fahrenheit, which is 0 degrees Celsius. A US forecast below 32 means ice is possible, and a forecast of 0 Fahrenheit is a very cold minus 17.7778 Celsius.

What is 350 degrees Fahrenheit in Celsius for an oven?

350 degrees Fahrenheit is 176.6667 degrees Celsius, usually written as 177 or rounded to 180 in European cookbooks. US recipes often use 350 Fahrenheit as the standard baking temperature.

Is minus 40 the same in Fahrenheit and Celsius?

Yes. Minus 40 is the one temperature where both scales agree: minus 40 Fahrenheit equals minus 40 Celsius. It is a useful check that a conversion is working, and a very cold day in either system.

How do I estimate Fahrenheit to Celsius in my head?

Subtract 30 and halve the result for a rough answer: 80 Fahrenheit minus 30 is 50, halved is 25 Celsius, close to the exact 26.6667. For cooking and weather the estimate is usually good enough, but use the converter for medicine and precise baking.

Which countries still use Fahrenheit?

The United States is the main country using Fahrenheit for everyday weather, cooking, and body temperature. A few other places, including the Bahamas, Belize, and the Cayman Islands, also use it, while the United Kingdom uses Celsius for weather but still hears Fahrenheit in some older contexts.

Sources

• NIST Special Publication 811 — Guide for the Use of the International System of Units (SI), including Celsius and Fahrenheit definitions.
• BIPM SI Brochure — The International System of Units, including the kelvin definition behind the Celsius scale (0 °C = 273.15 K).
• International Temperature Scale of 1990 (ITS-90) — the practical scale used to realise temperature measurements.

Disclaimer: Conversions are exact; for illness, follow the thermometer reading and local health guidance rather than any converted figure alone.

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