Fahrenheit to Celsius Converter

The °F to °C formula

Subtract 32 from the Fahrenheit temperature, then multiply by 5/9. To go back, multiply Celsius by 9/5 (that is, 1.8) and add 32. The 32 is there because water freezes at 32 °F but 0 °C; the 5/9 is there because the 180 Fahrenheit degrees between freezing and boiling cover the same range as 100 Celsius degrees.

°C = (°F − 32) × 5 ÷ 9
°F = °C × 9 ÷ 5 + 32

Worked examples

Example 1: a mild day at 72 °F

72 − 32 = 40, and 40 × 5 ÷ 9 = 22.22 °C.

Example 2: normal body temperature 98.6 °F

98.6 − 32 = 66.6, and 66.6 × 5 ÷ 9 = 37 °C. That traditional figure comes from 19th-century measurements; modern studies find typical adult averages slightly lower, and a normal reading varies by person, time of day and where it is taken.

Example 3: an oven at 425 °F

425 − 32 = 393, and 393 × 5 ÷ 9 = 218.33 °C, commonly written as 220 °C on recipes.

Example 4: Celsius back to Fahrenheit

A forecast of 28 °C: 28 × 9 ÷ 5 = 50.4, plus 32 = 82.4 °F.

Fahrenheit to Celsius chart

Celsius to Fahrenheit chart

The mental shortcut

Subtract 30 and halve: 72 °F → 42 ÷ 2 = 21 °C, against an exact 22.2 °C. In reverse, double and add 30: 20 °C → 70 °F against an exact 68 °F. The shortcut is within about 2 °C across everyday weather from freezing to the low 30s Celsius, but it drifts badly at oven temperatures — 400 °F becomes 185 °C by shortcut versus 204 °C exactly — so use the formula for cooking. The result panel prints the shortcut next to the exact answer so you can see the gap for your own number.

Common uses

The US, its territories and a handful of other countries use Fahrenheit for everyday temperatures, while almost everywhere else uses Celsius. That makes this conversion part of travel planning, reading recipes and appliance manuals, setting thermostats in rented homes abroad, following international weather news, checking a fever on a thermometer set to the unfamiliar scale, and caring for aquariums, greenhouses and home-brewing equipment. For kelvin and Rankine as well, use the full temperature converter.

Precision and rounding

Because of the 5/9 factor, most Fahrenheit values do not convert to tidy Celsius numbers, so the result is shown to two decimals and the table to two decimals as well. Round for the purpose: weather to the nearest degree, oven settings to the nearest 5 or 10 degrees as printed on the dial, and medical readings to one decimal place. When converting a change in temperature, such as "5 °F warmer", skip the 32 and just multiply by 5/9 — a 5 °F rise is about 2.8 °C. Values below absolute zero (−459.67 °F) are rejected.

Why some countries still use Fahrenheit

Fahrenheit was the standard in Britain and its colonies for most of the 19th and early 20th centuries. Most of those countries switched to Celsius as part of metrication between the 1960s and 1980s, while the United States kept Fahrenheit for weather, cooking and medicine even though its scientists use Celsius and kelvin. Supporters point out that the Fahrenheit scale's smaller degree gives finer whole-number steps for air temperature, and that 0 to 100 °F roughly spans the weather people experience in temperate climates. Whatever the merits, the two scales will coexist for the foreseeable future, so a quick converter remains handy.