Celsius to Fahrenheit formula
°F = (°C × 9⁄5) + 32 Example: 20°C × 9⁄5 = 36, + 32 = 68°F The simple mental math shortcut
If you need to estimate the temperature quickly in your head without a calculator, use this simple trick: Double the Celsius temperature, then add 30. While it won't give you the exact decimal point, it gets you incredibly close for everyday weather forecasts. For example, if it is 20°C outside: 20 doubled is 40, plus 30 gives you an estimate of 70°F (the exact answer is 68°F).
About the Celsius scale
The Celsius scale, originally called the centigrade scale, is part of the international metric system used by almost every country today. Developed by Swedish astronomer Anders Celsius in 1742, the scale is simple and logical because it is anchored completely to the behavior of water: 0°C is the exact point where water freezes, and 100°C is the exact point where it boils at sea level.
About the Fahrenheit scale
The Fahrenheit scale was created in 1724 by the physicist Daniel Gabriel Fahrenheit. It was the first standardized temperature scale to gain widespread popularity. On this scale, the freezing point of water is placed at 32°F and the boiling point is at 212°F, creating a precise 180-degree span between the two points. Today, it remains the standard temperature scale used primarily in the United States and its territories.
Reference table
| Celsius | Fahrenheit |
|---|---|
| −40°C | −40°F (the crossing point) |
| 0°C | 32°F (freezing) |
| 20°C | 68°F (room temperature) |
| 37°C | 98.6°F (body temperature) |
| 100°C | 212°F (boiling) |
Frequently asked questions
What is 20°C in Fahrenheit?
20°C is 68°F — a comfortable room temperature. Multiply by 9⁄5 (1.8) and add 32: 20 × 1.8 = 36, plus 32 = 68.
Why do Celsius and Fahrenheit meet at −40?
Both scales are linear, and −40 happens to be the exact point where their formulas cross — −40°C converts to exactly −40°F. It is the only temperature where the two scales agree.
What is normal body temperature in Fahrenheit?
The traditional reference is 98.6°F (37°C), though normal body temperature varies by person and time of day, typically ranging from about 97°F to 99°F.
Need the reverse direction? See Fahrenheit to Celsius.