Fahrenheit to Celsius
Convert Fahrenheit to Celsius with the exact formula (°F − 32) × 5/9, a quick reference table, and common everyday temperatures explained.
°F to °C formula
To convert Fahrenheit (°F) to Celsius (°C), subtract 32 and multiply by 5/9: °C = (°F − 32) × 5/9. Because the two scales meet at −40°, the offset of 32 and the ratio 5/9 line them up exactly.
Quick reference: °F to °C
Common values
0 °F = -17.78 °C
32 °F = 0 °C
50 °F = 10 °C
68 °F = 20 °C
77 °F = 25 °C
98.6 °F = 37 °C
100 °F = 37.78 °C
212 °F = 100 °C
Worked example
Convert 68 °F to Celsius:
(68 − 32) × 5/9 = 36 × 5/9 ≈ 20 °C
So 68 °F is about 20 °C.
Why convert °F to °C?
Most of the world reports weather, oven temperatures, and body temperature in Celsius. If you are reading a US forecast, recipe, or thermostat and need the metric value, this conversion gives it directly.
You can also use our calculator or read the paired guide °C reference.
Frequently Asked Questions
What is the formula from Fahrenheit to Celsius?
°C = (°F − 32) × 5/9. Subtract 32 first, then multiply by five-ninths.
Is 32 °F the same as 0 °C?
Yes. 32 °F is the freezing point of water, which equals 0 °C.
At what temperature are Fahrenheit and Celsius equal?
They are equal at −40°: −40 °F = −40 °C.
How do I convert 98.6 °F to Celsius?
(98.6 − 32) × 5/9 = 66.6 × 5/9 ≈ 37 °C, which is normal body temperature.
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Quick Summary
°F to °C uses a single exact factor. Use the formula above or the reference table for quick, accurate results.
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Disclaimer
Unit conversions on this site use internationally recognized, fixed conversion factors (for example, 1 inch = 2.54 cm, 1 pound = 0.45359237 kg, 1 °F = (°C × 9/5) + 32). They are provided for general, informational, and educational use. For applications where accuracy is critical — such as medical dosing, engineering, scientific research, trade, or legal compliance — always verify results against authoritative sources such as the U.S. National Institute of Standards and Technology (NIST) and the official International System of Units (SI) brochure, and follow any applicable local standards.
Exact Constants & Authoritative Sources
Every conversion on this page uses the fixed, internationally agreed constants below — drawn from NIST and the SI Brochure. No values are estimated or rounded as if exact. See the full list on our Sources & Standards page.
- EXACT°F = °C × 9/5 + 32 (exact linear relation)
- EXACT°C = (°F − 32) × 5/9 (exact inverse relation)
- EXACTKelvin (K) = °C + 273.15 (exact offset)
- EXACTWater freezes at 0 °C = 32 °F and boils at 100 °C = 212 °F
Common Pitfalls & How to Avoid Them
Subtract 32 BEFORE multiplying
°C = (°F − 32) × 5/9. Doing 5/9 × °F − 32 instead gives a wrong answer because the offset must be removed first. Parentheses matter.
Degrees are not the same size
A 1 °C step equals a 1.8 °F step. A "10-degree" forecast difference is 18 °F, not 10 °F. This is why a 5 °C day feels very different from a 15 °C day.
Negative signs
Below freezing, (°F − 32) is negative; keep the sign through the whole calculation. −40 °C = −40 °F is the only point where the two scales meet.
A unit-conversion reference site has no manufacturer-specific or device calibration parameters, so "layered tuning" does not apply here. The only real error-handling is input validation: the converter rejects non-numeric, empty, or out-of-range entries and shows a clear message, then falls back to exact constants above. No estimated or rounded figures are ever presented as exact.
Authoritative sources for this page
- NIST (U.S. National Institute of Standards and Technology) — NIST — SI Units: Temperature
Last Updated 2026 | This article was reviewed for accuracy