Fahrenheit To Celsius

This converter turns a temperature in degrees Fahrenheit into its Celsius equivalent the moment you type it in. It is the tool you need when a US weather forecast, an American recipe or a fever thermometer reading has to make sense in the Celsius terms the rest of the world uses. There is nothing to install and no formula to memorise — enter the Fahrenheit value and read the Celsius result straight away.

Quick Answer

To convert Fahrenheit to Celsius, subtract 32, then multiply by 5/9: °C = (°F − 32) × 5/9. For example, 98.6 °F works out to exactly 37 °C.

Where the Two Scales Come From

Fahrenheit and Celsius measure the same thing with different rulers. On the Celsius scale, water freezes at 0 °C and boils at 100 °C at standard atmospheric pressure, so the whole range between freezing and boiling spans 100 degrees. On the Fahrenheit scale those same two points sit at 32 °F and 212 °F, a span of 180 degrees. Because 180 Fahrenheit degrees cover the same interval as 100 Celsius degrees, each Celsius degree is worth 1.8 Fahrenheit degrees — which is where the 9/5 and 5/9 fractions in the formulas come from.

The subtraction of 32 exists because the scales do not start at the same place. Before you can compare sizes, you have to line up the zero points, and subtracting 32 shifts a Fahrenheit reading down to the Celsius starting line. Only then does the 5/9 rescaling give the right answer. This is also why the two scales meet at exactly one temperature: −40 °F and −40 °C are the same reading, a handy fact that surprises most people the first time they hear it.

Unlike a length or weight conversion, you cannot convert temperature by multiplying by one fixed factor alone. Any shortcut that skips the −32 step will be wrong everywhere except at −40. If you need the reverse journey, the Celsius to Fahrenheit converter applies the mirror-image formula.

How to Use the Fahrenheit to Celsius Converter

1. Find the temperature you want to convert, making sure it really is in Fahrenheit — US forecasts, older oven dials and many American thermometers use it by default.
2. Type the number into the input field. Decimals are fine, so a reading like 101.3 works just as well as a whole number.
3. Read the Celsius result, which appears as soon as the value is entered.
4. Check the size of the answer against a reference point you know: 68 °F should come out near 20 °C, and anything far from your expectation usually means a mistyped digit.
5. For a fever reading, remember that normal body temperature of 98.6 °F converts to 37 °C, and 100.4 °F converts to 38 °C, the threshold many doctors use for a fever.
6. Copy the result into your notes, recipe or message, keeping one decimal place for medical readings and whole numbers for weather.

A Fever Reading, Converted Step by Step

Suppose a thermometer shows 98.6 °F and you want to tell a doctor in Europe what that is in Celsius. Apply the formula in two moves. First subtract the offset: 98.6 − 32 = 66.6. Then rescale: 66.6 × 5/9 = 333 ÷ 9 = 37. So 98.6 °F = 37 °C, normal body temperature. The same two moves work for any reading: a child at 102 °F is at (102 − 32) × 5/9 = 38.9 °C, and water boiling at 212 °F is exactly 100 °C.

Reference points worth remembering:

• 32 °F = 0 °C — water freezes
• 50 °F = 10 °C — a cool spring day
• 68 °F = 20 °C — comfortable room temperature
• 86 °F = 30 °C — a hot summer day
• 104 °F = 40 °C — dangerously hot weather, or a high fever
• 212 °F = 100 °C — water boils
• −40 °F = −40 °C — the point where the two scales agree

Conversion Mistakes That Catch People Out

The most common error is multiplying by 5/9 without subtracting 32 first, which quietly shifts every result. A quick sanity check protects you: Celsius numbers for everyday weather are smaller than the Fahrenheit originals, so if your answer grew, something went wrong. The second trap is oven temperatures in recipes. A US recipe calling for 350 °F means about 177 °C — gas mark 4 — and rounding that to 180 °C is fine for most baking, but delicate dishes and candy making deserve the exact figure, since sugar stages change within a few degrees.

Rounding matters in medicine too. Report a converted fever to one decimal place; 38.9 °C and 39 °C can lead to different advice. Finally, be careful with negative values in winter: −4 °F is −20 °C, not −20 °F with a new label, and wind chill figures quoted in Fahrenheit convert with exactly the same formula as air temperature. Weather apps that show a "feels like" value in one scale can be checked against this converter like any other reading. For scientific work rather than weather, you may need Kelvin as well, which the Fahrenheit to Kelvin converter handles in one step.

For weather alone, travellers use a rough shortcut: subtract 30 from the Fahrenheit figure and halve the result. At 68 °F it gives (68 − 30) ÷ 2 = 19 °C against the exact 20 °C — close enough to decide on a jacket. But watch how the shortcut decays where accuracy matters: at body temperature it gives (98.6 − 30) ÷ 2 = 34.3 °C against the true 37 °C, an error large enough to hide a fever entirely. The shortcut works because it approximates both the offset and the ratio at once, and it degrades gracefully across the weather range; outside that range, and always for cooking temperatures, medicine and science, use the exact formula or this converter instead. Knowing both methods means you can estimate in your head at a glance and verify on this page in seconds.

Everyday Temperatures, No Calculator Required

Once you know the anchor points — 0, 10, 20, 30 and 37 °C against their Fahrenheit partners — most daily conversions can be estimated in your head and confirmed here in seconds. Travellers, cooks, parents checking a fever and anyone reading American instructions all run into this scale gap regularly, and this page removes it. You will find the rest of the family, including converters for Kelvin, weight, length and more, on the converters category page.