Temperature Converter

Temperature converter: Celsius, Fahrenheit, and Kelvin

This converter links the three temperature scales used worldwide: Celsius (°C), Fahrenheit (°F), and Kelvin (K). Unlike most unit conversions, temperature scales have different zero points as well as different degree sizes, so each conversion uses a formula rather than a single multiplier. Enter a reading on one scale and the other two are recomputed for you.

The conversion formulas

°F = (°C × 9/5) + 32
°C = (°F − 32) × 5/9
K  = °C + 273.15
°C = K − 273.15

The 9/5 (1.8) factor appears because a Fahrenheit degree is smaller than a Celsius degree: there are 180 Fahrenheit degrees between freezing and boiling water, but only 100 Celsius degrees over the same range.

Why three scales exist

Celsius is the everyday metric scale, pinned to water freezing at 0° and boiling at 100° at sea level. Fahrenheit, still standard in the United States, places freezing at 32° and boiling at 212°, giving finer whole-degree resolution for weather. Kelvin is the scientific absolute scale: it starts at absolute zero and uses the same degree size as Celsius, which is why scientists can switch between them by adding 273.15.

Reference temperatures across all three scales

• Absolute zero: −273.15°C = −459.67°F = 0 K
• Water freezes: 0°C = 32°F = 273.15 K
• Room temperature: 21°C = 70°F = 294.15 K
• Body temperature: 37°C = 98.6°F = 310.15 K
• Water boils (sea level): 100°C = 212°F = 373.15 K

Cooking and oven temperatures

Recipes cross these scales constantly. A "moderate" oven of 180°C is 356°F (often rounded to 350°F), and a hot 220°C oven is 428°F (rounded to 425°F). When following a recipe from another country, convert the oven temperature first — a 50-degree Fahrenheit error is easy to make and can ruin a bake.

The −40 crossover and mental shortcuts

Celsius and Fahrenheit meet at exactly −40°, the only temperature that reads the same on both scales. For fast everyday estimates, doubling the Celsius value and adding 30 gets you within a couple of degrees of the true Fahrenheit figure — handy for checking the weather without a calculator.

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