Celsius to Fahrenheit: The Exact Formula With Examples

The Formula

To convert Celsius to Fahrenheit:

Equivalently written as: °F = (°C × 1.8) + 32

Step by step:

1. Multiply the Celsius temperature by 9
2. Divide the result by 5
3. Add 32

Example — converting 25°C:

1. 25 × 9 = 225
2. 225 ÷ 5 = 45
3. 45 + 32 = 77°F

Common Temperature Conversions

The Reverse Formula: Fahrenheit to Celsius

To go the other way:

Example — converting 98.6°F (body temperature):

1. 98.6 − 32 = 66.6
2. 66.6 × 5 = 333
3. 333 ÷ 9 = 37°C

Mental Math Shortcuts

When you need a rough estimate without a calculator:

• Quick Celsius → Fahrenheit: Double the Celsius temperature and add 30. This gives a fast approximation. Example: 20°C → 20×2=40, 40+30=70°F. (Actual: 68°F — close enough for everyday use.)
• Quick Fahrenheit → Celsius: Subtract 30 from Fahrenheit and halve it. Example: 70°F → 70-30=40, 40÷2=20°C. (Actual: 21.1°C — reasonable approximation.)
• Anchor points to memorise: 0°C=32°F (freezing), 20°C=68°F (room temp), 37°C=98.6°F (body), 100°C=212°F (boiling).

Why Do We Have Two Temperature Scales?

Celsius (also called centigrade) was proposed by Anders Celsius in 1742 and places 0° at water's freezing point and 100° at its boiling point. It's intuitive and used by almost every country in the world.

Fahrenheit was proposed by Daniel Gabriel Fahrenheit in 1724 and is primarily used in the United States. Its zero point was based on a brine solution temperature, making it less intuitive but giving more granularity for everyday human temperatures (body temp is 98.6°F rather than 37°C).

For instant conversion of Celsius, Fahrenheit, Kelvin, and Rankine — ToolLance's Unit Converter handles all four in the Temperature tab, with the full offset formula rather than a linear approximation.