Fahrenheit to Celsius Calculator
Type any Fahrenheit temperature to get the exact Celsius equivalent, plus Kelvin and Rankine conversions. Common landmarks — freezing, body temperature, boiling point — are marked on the scale for reference.
°F
(°F − 32) × 5/9
- 1
Subtract the Fahrenheit offset
72 − 32 = 40 - 2
Scale to Celsius (× 5 ÷ 9)
40 × 5 ÷ 9 = 22.2222
How does this calculator work?
Fahrenheit to Celsius: °C = (°F − 32) × 5/9. Key references: 32 °F = 0 °C (freezing), 98.6 °F = 37 °C (body temp), 212 °F = 100 °C (boiling), −40 °F = −40 °C (the only point where both scales agree). Add 273.15 to the Celsius result to get Kelvin.
Formula
How this is calculated
The Fahrenheit and Celsius scales share the same reference points — the freezing and boiling points of water — but place them at different numbers and use different degree sizes. Water freezes at 32 °F and 0 °C; it boils at 212 °F and 100 °C. That means 180 Fahrenheit degrees span the same physical range as 100 Celsius degrees, so one Fahrenheit degree is 5/9 of a Celsius degree.
The conversion formula adjusts for both the size difference and the offset: subtract 32 (to shift the zero point from 32 °F to 0 °C) then multiply by 5/9 (to scale the degree size). Kelvin adds 273.15 to the Celsius result because it is an absolute scale with the same degree size as Celsius but zero at absolute zero (−273.15 °C). Rankine is the absolute version of Fahrenheit: it shares the Fahrenheit degree size but starts at absolute zero, so °R = °F + 459.67.
The conversion is exact — no approximation is involved. The only source of imprecision is the 273.15 offset in the Kelvin definition, which is exact by convention (the 2019 SI redefinition set 0 K ≡ −273.15 °C exactly).
Frequently asked questions
°C = (°F − 32) × 5/9. For quick mental arithmetic: subtract 32, divide by 2, then add 10% of that result. For example, 68 °F → (68 − 32) = 36 → 36 ÷ 2 = 18 → 18 + 1.8 = 19.8 °C (exact: 20 °C). The formula (°F − 32) × 5/9 is always exact.
At −40°. Setting °C = °F gives (F − 32) × 5/9 = F, which solves to F = −40. Both scales coincide at minus forty, which is also why −40 is used as a calibration check point.
The US adopted Fahrenheit in colonial times and never underwent the metric conversion that most countries completed in the 1960s–1980s. Familiarity and the cost of switching infrastructure keep it in everyday use for weather, cooking, and medicine, even as science and industry in the US use Celsius and Kelvin.
Also known as
TG we-Calculate Editorial Team. (2026). Fahrenheit to Celsius Calculator [Online calculator]. TG we-Calculate. https://we-calculate.com/calculator/fahrenheit-to-celsius-calculator
TG we-Calculate Editorial Team. "Fahrenheit to Celsius Calculator." TG we-Calculate. 2026. https://we-calculate.com/calculator/fahrenheit-to-celsius-calculator.
TG we-Calculate Editorial Team, "Fahrenheit to Celsius Calculator," TG we-Calculate, 2026. [Online]. Available: https://we-calculate.com/calculator/fahrenheit-to-celsius-calculator
@misc{wecalculate_fahrenheit_to_celsius_calculator, title = {Fahrenheit to Celsius Calculator}, author = {{TG we-Calculate Editorial Team}}, howpublished = {\url{https://we-calculate.com/calculator/fahrenheit-to-celsius-calculator}}, year = {2026}, note = {TG we-Calculate} }
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