Celsius to Fahrenheit: Formula, Chart & Quick Reference
The Celsius to Fahrenheit formula is F = (C × 9/5) + 32. Here's how to use it, a full reference chart from -40°C to 100°C, and memory shortcuts for the most common temperatures.
The Conversion Formula
To convert Celsius to Fahrenheit:
°F = (°C × 9/5) + 32
Or equivalently: °F = (°C × 1.8) + 32
To convert Fahrenheit to Celsius (the reverse):
°C = (°F − 32) × 5/9
Or: °C = (°F − 32) ÷ 1.8
Use our Unit Converter for instant temperature conversion along with length, weight, volume, and more.
Worked Examples
Convert 25°C to Fahrenheit: (25 × 9/5) + 32 = 45 + 32 = 77°F
Convert 100°C to Fahrenheit: (100 × 9/5) + 32 = 180 + 32 = 212°F (boiling point of water)
Convert 98.6°F to Celsius: (98.6 − 32) × 5/9 = 66.6 × 0.5556 = 37°C (normal body temperature)
Convert −40°F to Celsius: (−40 − 32) × 5/9 = −72 × 0.5556 = −40°C (the one temperature where both scales meet)
Quick Reference Chart: Common Temperatures
| Celsius | Fahrenheit | Context |
|---|---|---|
| −40°C | −40°F | Extreme cold (both scales converge) |
| −18°C | 0°F | Typical US freezer temperature |
| 0°C | 32°F | Water freezes |
| 10°C | 50°F | Cool autumn day |
| 20°C | 68°F | Comfortable indoor temperature |
| 25°C | 77°F | Warm spring day |
| 30°C | 86°F | Hot summer day |
| 37°C | 98.6°F | Normal human body temperature |
| 40°C | 104°F | Heat wave / high fever threshold |
| 100°C | 212°F | Water boils (at sea level) |
Full Reference Chart: −40°C to 100°C
| °C | °F | °C | °F | °C | °F | ||
|---|---|---|---|---|---|---|---|
| −40 | −40 | 0 | 32 | 40 | 104 | ||
| −30 | −22 | 5 | 41 | 50 | 122 | ||
| −20 | −4 | 10 | 50 | 60 | 140 | ||
| −10 | 14 | 15 | 59 | 70 | 158 | ||
| −5 | 23 | 20 | 68 | 80 | 176 | ||
| −1 | 30 | 25 | 77 | 90 | 194 | ||
| 30 | 86 | 100 | 212 |
Memory Shortcuts
If you don't want to do algebra in your head, these benchmarks are worth memorizing:
- 0°C = 32°F (freezing)
- 10°C ≈ 50°F (cool)
- 20°C ≈ 68°F (comfortable)
- 30°C ≈ 86°F (hot)
- 37°C = 98.6°F (body temperature)
- 100°C = 212°F (boiling)
Quick mental approximation: Double the Celsius and add 30. This gives an answer within 1–2°F for everyday temperatures (0°C–30°C). For 22°C: 22 × 2 + 30 = 74°F (exact is 71.6°F — close enough for most purposes).
Why Two Scales Exist
Fahrenheit was developed by Daniel Gabriel Fahrenheit in 1724, calibrated around brine freezing (0°F) and average human body temperature (96°F in his original scale). It was the dominant scale in English-speaking countries for 200+ years.
Celsius (originally Centigrade) was developed by Anders Celsius in 1742, anchored at 0° for water freezing and 100° for water boiling — a more scientifically logical choice. It's now the global standard except in the US, which still uses Fahrenheit for everyday temperatures.
Conclusion: Key Takeaways
- Formula: °F = (°C × 9/5) + 32 | Reverse: °C = (°F − 32) × 5/9
- Key benchmarks: 0°C = 32°F, 100°C = 212°F, 37°C = 98.6°F
- Quick mental trick: Double the Celsius, add 30 — accurate to within 2°F for common temps
- −40° is the one temperature where Celsius and Fahrenheit are identical