Fahrenheit to Celsius Converter
Quick answer: Subtract 32 from the Fahrenheit reading and multiply by 5/9 to get Celsius — for example, 72°F is 22.2°C. To go the other way, multiply Celsius by 9/5 and add 32. Kelvin is Celsius plus 273.15, so 72°F is also 295.4 K.
This free Fahrenheit-to-Celsius converter translates temperatures both directions instantly and shows the Kelvin equivalent too. Type in either box and everything recalculates as you type.
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How to use this calculator
Type a temperature in the Fahrenheit box and the Celsius box fills in immediately, with Kelvin shown in the results table. Type in the Celsius box instead and Fahrenheit converts back. Negative values are fine — winter temperatures and freezer settings live below zero.
How this is calculated
Formulas: °C = (°F − 32) × 5/9 · °F = °C × 9/5 + 32 · K = °C + 273.15. Results are shown rounded to one decimal place.
Input definitions: “°F” and “°C” are temperatures on the Fahrenheit and Celsius scales; negative values are valid. Assumptions: the formulas are definitions of the scales themselves, so conversions are exact up to display rounding.
Worked example
72°F → Celsius: (72 − 32) × 5/9 = 40 × 5/9 = 22.2°C. To Kelvin: 22.222… + 273.15 = 295.4 K (rounded to one decimal). In reverse: 22.222… × 9/5 + 32 = 72°F.
Reference data
| Reference point | °F | °C | K |
|---|---|---|---|
| Water freezes | 32 | 0 | 273.15 |
| Room temperature | 68 | 20 | 293.15 |
| Human body | 98.6 | 37 | 310.15 |
| Water boils | 212 | 100 | 373.15 |
Body temperature of 98.6°F = 37°C is the conventional reference value; individual readings vary.
Source: derived from the defined conversion formulas (Fahrenheit scale fixed points 32°F/212°F; Celsius fixed points 0°C/100°C; kelvin offset 273.15), 2026.
Method & sources
The calculator applies the defining relations of the three scales: the two linear formulas between °F and °C and the fixed 273.15 offset to kelvin. Because these are definitions rather than measurements, every conversion is exact to the displayed precision.
- BIPM SI Brochure — kelvin defined by the 273.16 K triple point of water, giving the 273.15 offset to the Celsius scale
- NIST — Fahrenheit and Celsius scale definitions and conversion relations
No estimates appear on this page; all figures are definitional or direct arithmetic.
Frequently asked questions
Why are water’s freezing and boiling points 32°F and 212°F?
The Fahrenheit scale is defined today by water’s freezing point at 32°F and boiling point at 212°F at standard atmospheric pressure, while the Celsius scale puts the same two points at 0°C and 100°C. The conversion formulas are defined directly from those fixed points, so there is no approximation involved.
Is there a temperature where Fahrenheit and Celsius are the same?
Yes: −40°. Plugging it in, (−40 − 32) × 5/9 = −72 × 5/9 = −40, so −40°F equals −40°C — the only point where the two scales meet.
How do I convert to Kelvin?
Add 273.15 to the Celsius value: K = °C + 273.15. Kelvin starts at absolute zero, so 0 K = −273.15°C and Kelvin temperatures are never negative.