Fahrenheit to Celsius Converter
Convert Fahrenheit to Celsius using C = (F − 32) × 5/9, or switch to convert Celsius to Fahrenheit. Enter a temperature in °F or °C and read the result plus Kelvin.
Example: with Temperature 98.6 · Direction Fahrenheit → Celsius → Result: 37 °C.
- In Kelvin310.15 K
- FormulaC = (F − 32) × 5/9
Computed by the calculator below using its default values. Change any input to see your own numbers.
C = (F − 32) × 5/9 and F = C × 9/5 + 32. The scales cross at −40°, where Fahrenheit and Celsius read the same number.
How the two scales relate
Fahrenheit and Celsius disagree on two things: where zero sits and how big a degree is. Celsius puts 0 at water's freezing point and 100 at boiling. Fahrenheit puts those same points at 32 and 212, so 180 Fahrenheit degrees span the same range as 100 Celsius degrees. That gives the ratio 180/100 = 9/5.
To convert Fahrenheit to Celsius you first remove the 32-degree offset, then scale by 5/9: C = (F − 32) × 5/9. Skipping the subtraction is the classic error — it throws the answer off by nearly 18 degrees. The scales meet at −40°, a handy checkpoint: if your formula gives −40 °C for −40 °F, you did it right.
How it’s calculated
C = (F − 32) × 5/9; F = C × 9/5 + 32. Kelvin is Celsius + 273.15. The 9/5 ratio comes from 180 Fahrenheit degrees spanning the same interval as 100 Celsius degrees between water's freezing and boiling points. Results round to 2 decimals.
Standard temperature scales. Kelvin uses the exact 273.15 offset; no pressure or humidity correction is involved.
Fahrenheit and Celsius reference
| Fahrenheit | Celsius | What it is |
|---|---|---|
| −40 °F | −40 °C | Scales meet |
| 32 °F | 0 °C | Water freezes |
| 68 °F | 20 °C | Room temperature |
| 98.6 °F | 37 °C | Body temperature |
| 212 °F | 100 °C | Water boils |
Computed with C = (F − 32) × 5/9.
Common mistakes
- Forgetting to subtract 32 first — multiplying by 5/9 alone can be off by nearly 18 degrees.
- Using 1.8 to divide instead of multiply, or vice versa, when reversing the formula.
- Rounding 5/9 to 0.5 for mental math, which drifts noticeably at high temperatures.
Frequently asked questions
What is the Fahrenheit to Celsius formula?
C = (F − 32) × 5/9. Subtract 32 from the Fahrenheit value, then multiply by 5 and divide by 9.
What is 98.6 °F in Celsius?
(98.6 − 32) × 5/9 = 37 °C, the standard normal body temperature.
At what temperature do the scales read the same?
At −40°. Minus 40 Fahrenheit equals minus 40 Celsius exactly — a useful check on any conversion.
How do I convert Celsius back to Fahrenheit?
Use F = C × 9/5 + 32. Multiply by 9/5 first, then add 32. For example, 20 °C becomes 68 °F.