C to F Formula
The Celsius to Fahrenheit Formula
Converting Celsius to Fahrenheit uses one straightforward equation:
°F = (°C × 9/5) + 32
You can also multiply by 1.8 instead of 9/5 – both give the same result.
The constant 32 appears because water freezes at 32°F but 0°C. The factor 9/5 (or 1.8) accounts for the different size of a degree on each scale: a change of 1°C equals a change of 1.8°F.
For example, 25°C becomes:
(25 × 9/5) + 32 = 45 + 32 = 77°F.
Need a faster way? The calculator below converts any Celsius value to Fahrenheit instantly.
Step-by-Step Conversion Examples
Work through a few common temperatures to see the formula in action.
0°C – freezing point of water
(0 × 9/5) + 32 = 0 + 32 = 32°F
100°C – boiling point of water
(100 × 9/5) + 32 = 180 + 32 = 212°F
37°C – average human body temperature
(37 × 9/5) + 32 = 66.6 + 32 = 98.6°F
For medical measurements, always rely on a properly calibrated thermometer; these values are approximate.
−40°C – where the scales meet
(−40 × 9/5) + 32 = −72 + 32 = −40°F
At −40 degrees, both scales read the same number.
Celsius to Fahrenheit Conversion Table
Refer to this table for quick look‑ups of everyday temperatures.
| Celsius (°C) | Fahrenheit (°F) |
|---|---|
| −50 | −58 |
| −40 | −40 |
| −30 | −22 |
| −20 | −4 |
| −10 | 14 |
| 0 | 32 |
| 10 | 50 |
| 20 | 68 |
| 30 | 86 |
| 40 | 104 |
| 50 | 122 |
| 100 | 212 |
Quick Mental Conversion Trick
When you need only an approximate value, double the Celsius number and add 30.
- 20°C → 20 × 2 + 30 = 70°F (exact 68°F, error ±2°F)
- 10°C → 10 × 2 + 30 = 50°F (exact 50°F, no error here)
The trick works best for mild weather temperatures. For precise work, always apply the exact formula.
Reverse Conversion: Fahrenheit to Celsius
To go from Fahrenheit to Celsius, rearrange the formula:
°C = (°F − 32) × 5/9
or divide by 1.8 after subtracting 32.
Example: 86°F
(86 − 32) × 5/9 = 54 × 5/9 = 30°C.
This reverse formula covers everything from cooking temperatures to weather reports. Use the calculator above for instant conversion in either direction.