How to Convert Between Fahrenheit and Celsius

The quick way to make sense of Fahrenheit values you'll see in US sources.

Summary

While most of the world uses Celsius, the US still runs on Fahrenheit. Rather than memorizing the formula, it's faster to use a conversion tool whenever you hit a Fahrenheit value in a weather report, a recipe, or a product spec.

Step by step

Note the temperature value and its unit (°F or °C) you're working with.
Enter the value into a temperature conversion tool instead of memorizing the formula.
When rounding the result, keep decimal precision in a medical or scientific context.
Keeping a few reference points in mind (0°C=32°F, 100°C=212°F) helps with quick everyday estimates.

Why it matters

Outside the US, you mostly run into Fahrenheit in recipes, manuals for American appliances, weather forecasts before a trip, and health content from US sources. Missing the unit can be merely confusing or it can cause real trouble, like trying to set an oven to 350 degrees Celsius for a cake, or misreading a body temperature of 100 degrees.

The formula and a few anchors

To go from Celsius to Fahrenheit, multiply by 9, divide by 5, and add 32. To go back, subtract 32 first, then multiply by 5 and divide by 9. For a rough mental estimate, double the Celsius value and add 30. It's close at everyday temperatures but drifts further off as values climb.

37°C, normal body temperature, is 98.6°F.
180°C oven heat is 356°F, usually written as 350°F in recipes.
20°C room temperature is 68°F.
At -40, both scales read the same.

Common mistakes

Doing the steps in the wrong order, adding 32 before multiplying.
Adding 32 when converting a temperature difference. A 10-degree Celsius change equals an 18-degree Fahrenheit change, with no 32 involved.
Trying to match an oven setting to the exact decimal. Rounding by 5 or 10 degrees is fine for a home oven.
Confusing Kelvin with Fahrenheit. A K in a scientific text is a separate scale.

A sample scenario

An American cookie recipe says to preheat the oven to 375°F. Run through the formula, that's about 190.6°C. The oven dial moves in 10-degree steps, so 190°C is close enough. The same recipe wants butter at 65°F, roughly 18°C, which means butter that's been out of the fridge for a while but isn't soft.

When to check with a professional

If a thermometer bought abroad reads in Fahrenheit and you're unsure how to interpret a fever reading after converting it, ask a healthcare professional. With babies and young children especially, don't guess.