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Fahrenheit (°F)

Also called: °F, degree Fahrenheit

Definition: Fahrenheit is the temperature scale used for everyday weather and cooking in the United States; a degree is 5/9 the size of a Celsius degree, and 32 °F equals 0 °C.

Updated November 3, 2026 · How we check facts

The degree Fahrenheit (°F) is the temperature unit of US customary use. NIST gives the conversion to the kelvin as K = (°F + 459.67) ÷ 1.8, and the Celsius form as °C = (°F − 32) ÷ 1.8. A change of one degree Fahrenheit equals 0.5555556 K, so the Fahrenheit degree is the smaller one.

Formula

°F = °C × 1.8 + 32
°C = (°F − 32) ÷ 1.8

Example

Water freezes at 32 °F, which is 0 °C, and boils at 212 °F, which is (212 − 32) ÷ 1.8 = 100 °C at standard pressure. A hot day of 95 °F is (95 − 32) ÷ 1.8 = 35 °C. A cold day of 14 °F is −10 °C, and −40 is the same in both scales.

Use the Celsius to Fahrenheit converter or the guide; the Celsius side is explained under Celsius.

Common mistake

Do not convert a temperature difference with the +32 step: a rise of 10 °C is a rise of 18 °F (10 × 1.8), not 50 °F.

Calculate it

Free toolCelsius to Fahrenheit Converter°C to °F and back, with the formula shown.

Guides that explain it

Related terms

Celsius (°C)Celsius is a temperature scale in which one degree has the same size as one kelvin, with 0 °C equal to 273.15 K; water freezes near 0 °C and boils near 100 °C at standard pressure.Kelvin (K)The kelvin is the SI base unit of temperature. It starts at absolute zero (0 K), and one kelvin is the same size as one degree Celsius, with 0 °C equal to 273.15 K.Absolute ZeroAbsolute zero is 0 K, the lowest point of the kelvin temperature scale. On the Celsius scale it equals −273.15 °C, and on the Fahrenheit scale about −459.67 °F.Greatest Common Factor (GCF)The greatest common factor (GCF) of two or more positive integers is the largest whole number that divides each of them with no remainder; it is also called the GCD or HCF.International System of Units (SI)The International System of Units (SI) is the modern metric system: seven base units, including the meter, kilogram, second and kelvin, with prefixes that scale by powers of ten.Least Common Multiple (LCM)The least common multiple (LCM) of two or more positive integers is the smallest positive number that each of them divides into evenly; it gives the lowest common denominator.Mixed NumberA mixed number combines a whole number and a proper fraction, such as 4 9/100; it equals an improper fraction, here 409/100, and is what a decimal with a nonzero whole part converts to.Percent ChangePercent change is the difference between a new and an original value, divided by the original value and expressed as a percentage; a positive result is an increase and a negative one a decrease.

Sources

  1. NIST Guide to the SI (SP 811), Appendix B.8 — Factors for Units Listed Alphabetically