CONVERSIONS

Convert between Celsius, Fahrenheit, and Kelvin. Enter a temperature and pick the units.

Temperature

From

Converted

—

In the target scale.

Usage Tip

Quick Fahrenheit-to-Celsius estimate: subtract 30 and halve it. For Celsius-to-Fahrenheit, double it and add 30. It is rough but close enough for weather.

THE MATH

To Celsius: F → (F − 32) × 5/9, K → K − 273.15
From Celsius: C × 9/5 + 32 = F, C + 273.15 = K

Celsius and Fahrenheit are offset scales (they cross at −40°), while Kelvin is Celsius shifted so 0 sits at absolute zero.
Water freezes at 0°C / 32°F / 273.15K and boils at 100°C / 212°F at sea level.

Temperature conversion is not a simple ratio — the scales have different zero points, so you cannot just multiply.
Kelvin has no negative values; absolute zero (0K) is the coldest possible temperature.
A change of 1°C equals a change of 1K and of 1.8°F.

Practical Notes

Celsius, Fahrenheit, and Kelvin measure temperature on different scales. Water freezes at 0 degrees Celsius, 32 degrees Fahrenheit, and 273.15 kelvin, and it boils at 100 degrees Celsius, 212 degrees Fahrenheit, and 373.15 kelvin at standard pressure.

To convert Celsius to Fahrenheit, multiply by 9 over 5 and add 32. To go back, subtract 32 and multiply by 5 over 9. Kelvin is Celsius plus 273.15, and it has no negative values because zero kelvin is absolute zero. A change of one degree is the same size in Celsius and kelvin, while a Fahrenheit degree is smaller, at five ninths of a Celsius degree.

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