Converting Celsius to Fahrenheit is the most common temperature conversion (travel to the US, Anglo recipes, international news). Here you have the exact formula, a ready-to-print table and a mental trick to estimate without a calculator.
Exact formula
°F = (°C × 9/5) + 32
°F = °C × 1.8 + 32 (decimal form)
Examples:
- 0 °C → 0 × 1.8 + 32 = 32 °F
- 20 °C → 20 × 1.8 + 32 = 68 °F
- 37 °C → 37 × 1.8 + 32 = 98.6 °F
- 100 °C → 100 × 1.8 + 32 = 212 °F
Quick reference table (°C → °F)
| °C | °F | Context |
|---|---|---|
| -40 | -40 | Crossing point (same in both) |
| -30 | -22 | Extreme cold |
| -20 | -4 | Home freezer |
| -10 | 14 | Hard winter |
| 0 | 32 | Water freezes |
| 5 | 41 | Fridge |
| 10 | 50 | Cool day |
| 15 | 59 | Mild spring |
| 20 | 68 | Indoor comfort |
| 22 | 71.6 | Ideal home temp |
| 25 | 77 | Warm summer |
| 30 | 86 | Hot |
| 35 | 95 | Heat wave |
| 37 | 98.6 | Body temperature |
| 38 | 100.4 | Fever |
| 40 | 104 | High fever |
| 50 | 122 | Very hot water |
| 100 | 212 | Water boils |
Mental trick: “Double and add 30”
°F ≈ °C × 2 + 30
| °C | Trick | Exact | Error |
|---|---|---|---|
| 0 | 30 | 32 | -2 |
| 10 | 50 | 50 | 0 |
| 20 | 70 | 68 | +2 |
| 25 | 80 | 77 | +3 |
| 30 | 90 | 86 | +4 |
| 35 | 100 | 95 | +5 |
Validity: error < 2 °F between 5 and 25 °C (comfort range). Outside that, use the exact formula or the temperature converter.
Inverse: Fahrenheit to Celsius
°C = (°F − 32) × 5/9
°C = (°F − 32) / 1.8
Mental inverse trick: subtract 30 and divide by 2 (°C ≈ (°F − 30) / 2). Same validity range.
Kelvin (bonus)
K = °C + 273.15
°C = K − 273.15
Absolute zero (0 K) = −273.15 °C = −459.67 °F.
Conclusion
- Exact: °F = °C × 1.8 + 32 (always).
- Mental: double °C and add 30 (only 0–35 °C).
- Table: print the one above for fridge / suitcase.
- Tool: unit converter for any value instantly.