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Celsius, Fahrenheit, and Kelvin formulas
The three common temperature scales use different zero points and step sizes. Celsius is widely used for weather and everyday temperatures, Fahrenheit is common in the United States, and Kelvin is used in science as an absolute temperature scale. Kelvin values are written without a degree sign.
Conversion formulas
From Celsius: °F = °C × 9/5 + 32 and K = °C + 273.15. To convert Fahrenheit to Celsius, use °C = (°F − 32) × 5/9; then add 273.15 to convert Celsius to Kelvin.
Worked example
Water freezes at 0°C, which is 32°F or 273.15 K. Water boils at 100°C, which is 212°F or 373.15 K at standard atmospheric pressure. The boiling point changes with pressure, so that example is not universal at high elevations or in pressurized systems.
The converter rounds displayed values to four decimal places. For laboratory work, engineering, or safety-critical measurements, use the precision and reference conditions required by the applicable standard.
Tips for accurate results
Fahrenheit equals Celsius × 9/5 + 32, and Kelvin equals Celsius + 273.15. Water freezes at 0°C (32°F) and boils at 100°C (212°F) at sea level. A change of 1°C equals a change of 1.8°F, but the scales start at different zero points.
Common mistakes and limits
Do not convert temperature differences with the full formula. A 10-degree rise in Celsius is an 18-degree rise in Fahrenheit, not 50. Nothing can be colder than absolute zero, which is 0 K or about −273.15°C.
Learn more: Unit conversion: common mistakes and how to avoid them.