How to Convert Celsius to Fahrenheit

Celsius and Fahrenheit are interval scales with different zero points, so a conversion needs both a ratio and an offset. A Fahrenheit degree is 5/9 the size of a Celsius degree, and 0 °C sits at 32 °F.

The formula

°F = (°C × 9/5) + 32 and °C = (°F − 32) × 5/9

Worked examples

• 20 °C × 9/5 = 36, plus 32 = 68 °F
• 37 °C × 9/5 = 66.6, plus 32 = 98.6 °F (normal body temperature)
• 180 °C × 9/5 = 324, plus 32 = 356 °F (a moderate oven)
• −40 °C = −40 °F — the one point where the two scales meet

A mental shortcut

Double the Celsius value and add 30. For 20 °C that gives 70 °F against a true 68 °F — close enough for weather, though never for cooking, medicine or engineering.

Common temperatures

Where each scale is used

Fahrenheit remains the everyday scale in the United States. The United Kingdom, Canada, Australia and New Zealand all report weather in Celsius, although older UK ovens and some US-imported recipes still use Fahrenheit. Scientific work uses Celsius or kelvin.