How to convert Celsius to Fahrenheit, from ovens to weather

01

How to convert Celsius to Fahrenheit

To convert Celsius to Fahrenheit, multiply by 1.8 and add 32. You may also see it written as × 9/5 + 32; 9/5 and 1.8 are the same number. The formula is exact, so the answer is as precise as the temperature you start with.

1. Multiply by 1.8

   25 °C × 1.8 = 45.

2. Add 32

   45 + 32 = 77. So 25 °C is 77 °F.

02

How to convert Celsius to Fahrenheit in your head

Double the Celsius number and add 30. That lands within a few degrees for weather, but it is far off for an oven.

The shortcut uses 2 instead of 1.8, and 30 instead of 32. At 10 °C the two errors cancel out. Every degree above 10 °C adds 0.2 °F of error, and every degree below takes 0.2 °F away. By 180 °C the shortcut is 34 °F too hot. Use it for the forecast, not for baking.

03

Oven temperatures: 160, 180, 200 and 220 °C in Fahrenheit

160 °C is 320 °F, 180 °C is 356 °F, 200 °C is 392 °F and 220 °C is 428 °F. The chart below covers 140 to 250 °C in steps of 10.

If your oven dial is marked in 25 °F steps, set the closest mark, which is in the right column. One row needs care: 170 °C is 338 °F, almost exactly between 325 and 350 °F (13 °F above 325 and 12 °F below 350). If you are unsure, check the food a few minutes before the recipe’s time.

04

Weather temperatures: 20, 22, 30 and 40 °C in Fahrenheit

20 °C is 68 °F, 22 °C is 71.6 °F, 30 °C is 86 °F and 40 °C is 104 °F. The chart covers −20 to 45 °C in steps of 5.

Below zero, keep the minus sign when you multiply. −10 °C × 1.8 = −18, and −18 + 32 = 14 °F. At −40 the two scales meet: −40 °C is −40 °F.

37 °C converts to 98.6 °F. That is a pure conversion of the number. This guide does not interpret body temperatures.

05

Fahrenheit to Celsius: the reverse formula

To convert Fahrenheit to Celsius, subtract 32 first, then divide by 1.8 (or multiply by 5/9). The order matters: subtract first, then divide.

1. Subtract 32

   350 − 32 = 318.

2. Divide by 1.8

   318 ÷ 1.8 = 176.67. So 350 °F is about 176.7 °C.

06

Common mistakes when converting oven temperatures

The slip to watch for first is adding 32 before multiplying. Here are the mistakes that give a wrong number, and how to avoid each one.

• Adding before multiplying. (180 + 32) × 1.8 = 381.6, which is 25.6 °F too hot. Multiply first, then add.
• Converting a change as if it were a temperature. If a recipe says “turn the oven up by 10 °C”, that is 10 × 1.8 = 18 °F more, not 50 °F. The +32 belongs to temperatures, not to differences.
• Using the head shortcut for baking. At 180 °C it gives 390 °F, 34 °F more than the real 356 °F.
• Rounding twice. Convert from the recipe’s own number, not from a value you have already rounded.
• Trusting the dial blindly. A dial setting is a target, not a measurement. If results look wrong, a separate oven thermometer shows what the oven actually reaches.