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How do I convert Celsius to Fahrenheit?

Short answer

Multiply by 9/5, then add 32: F = C x 9/5 + 32. For example, 25 C x 9/5 is 45, plus 32 makes 77 F. A free converter runs the formula instantly for any temperature.

The formula, worked through

F = C x 9/5 + 32. The 9/5 stretches Celsius degrees into the finer Fahrenheit scale, and the plus 32 shifts the freezing point. Worked example: 30 C x 9/5 = 54, plus 32 = 86 F, a hot summer day. Body temperature: 37 C x 9/5 = 66.6, plus 32 = 98.6 F.

Anchor points

0 C is 32 F, 20 C is 68 F, 30 C is 86 F, 37 C is 98.6 F, 40 C is 104 F and 100 C is 212 F. A rough mental shortcut for weather is to double the Celsius figure and add 30, which turns 25 C into 80 against the true 77 F, close enough for deciding on a jacket.

Frequently asked questions

What is 37 C in Fahrenheit?

98.6 F: 37 x 9/5 = 66.6, plus 32 gives 98.6.

What is 40 C in Fahrenheit?

104 F: 40 x 9/5 = 72, plus 32 gives 104.

Is doubling and adding 30 accurate?

It is a rough estimate. It gives 80 for 25 C where the true answer is 77 F. Use the exact formula or the converter when the number matters.

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