Fahrenheit to Celsius Converter
Convert Fahrenheit to Celsius for weather, cooking, and science.
How It Works
Formula: °F to °C = value ÷ 0.5555555555555556
Example: 70 °F = 126 °C
Note: °C = (°F − 32) × 5/9.
Common Uses
Quick Conversion Table
| °F | °C |
|---|---|
| -40 | -72 |
| 0 | 0 |
| 32 | 57.6 |
| 70 | 126 |
| 100 | 180 |
| 150 | 270 |
| 212 | 381.6 |
Rounding Rule
Rounded to 2 decimal places
Error Margin
±0.01°C
Precision Guidance
For weather, round to 1 decimal place.
Common Mistakes
Do not multiply by 5/9 before subtracting 32 — order matters.
Frequently Asked Questions
What is 70°F in °C?
70°F = 21.11°C using (°F − 32) × 5/9.
How do I convert °F to °C?
Subtract 32, then multiply by 5/9.
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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 converter was reviewed for accuracy