How to convert Celsius to Fahrenheit (and back)

The exact formulas, a quick mental shortcut, and a table of everyday temperatures.

Most of the world measures temperature in Celsius (°C), while the United States mostly uses Fahrenheit (°F). Converting between them takes one multiplication and one addition. Celsius to Fahrenheit °F = °C × 1.8 + 32 (1.8 is the same as 9/5). Example: 25 °C × 1.8 = 45, and 45 + 32 = 77 °F. Fahrenheit to Celsius °C = (°F − 32) ÷ 1.8 (the same as multiplying by 5/9). Example: 98.6 °F − 32 = 66.6, and 66.6 ÷ 1.8 = 37 °C. A quick mental shortcut Double the Celsius number and add 30. 20 °C becomes about 70 °F (the exact answer is 68 °F). The shortcut is close for everyday weather and drifts further off when it is very hot or very cold. Going the other way, subtract 30 from the Fahrenheit number and halve it. Everyday temperatures Oven temperatures Recipes round oven settings to friendly numbers, so the pairs below are the usual matches rather than exact conversions: Fan (convection) ovens If your oven has a fan, recipes often suggest setting it about 20 °C (or 25 °F) lower than a standard oven, because moving air cooks food faster. Check your oven’s manual, since models differ. Weather in both scales Below 0 °C (32 °F), water freezes and roads can ice over. Between about 15 °C and 25 °C…