Maths⏱ 4 min read

How to Convert Between Celsius, Fahrenheit and Kelvin

Temperature conversion trips people up constantly. Here are the exact formulas, quick mental maths shortcuts, and a reference table for the most common values.

Whether you're baking from an American recipe, reading a scientific paper, or just confused by a weather forecast, temperature conversion is a skill worth having locked in. Here are all three scales and how to move between them.

The Three Scales

Celsius (°C) is the international standard used in science and most of the world. Water freezes at 0°C and boils at 100°C.

Fahrenheit (°F) is used primarily in the United States. Water freezes at 32°F and boils at 212°F.

Kelvin (K) is the scientific absolute temperature scale. 0K is absolute zero — the theoretical temperature at which all molecular motion stops. There are no negative Kelvin values. Water freezes at 273.15K.

The Conversion Formulas

Celsius to Fahrenheit: °F = (°C × 9/5) + 32 Fahrenheit to Celsius: °C = (°F − 32) × 5/9 Celsius to Kelvin: K = °C + 273.15 Kelvin to Celsius: °C = K − 273.15 Fahrenheit to Kelvin: K = (°F − 32) × 5/9 + 273.15

Quick Mental Maths Shortcuts

The exact formulas require a calculator. These shortcuts are close enough for everyday use:

Essential Reference Table

SituationCelsiusFahrenheit
Absolute zero−273.15°C−459.67°F
Water freezes0°C32°F
Cold winter day−5°C23°F
Cool room18°C64°F
Comfortable room21°C70°F
Warm summer day28°C82°F
Hot day35°C95°F
Body temperature37°C98.6°F
Fever38.5°C101.3°F
Oven: gas mark 4180°C356°F
Oven: gas mark 7220°C428°F
Water boils (sea level)100°C212°F

Cooking Temperature Conversions

American recipes use Fahrenheit oven temperatures. Here are the most common, including fan vs conventional adjustments:

FahrenheitCelsius (Conventional)Celsius (Fan)
300°F150°C130°C
325°F160°C140°C
350°F175°C155°C
375°F190°C170°C
400°F200°C180°C
425°F220°C200°C
450°F230°C210°C

Fan-assisted ovens circulate air and cook more efficiently. The standard adjustment is to reduce the temperature by 20°C (about 25°F) compared to a conventional oven setting.

🌡️
Try it yourself — free
Temperature Converter · no sign-up, instant results
Open Temperature Converter →
← All Articles