Convert between Fahrenheit, Celsius and kelvin with the exact formulas. Negative temperatures work, down to absolute zero — anything colder is flagged.
Temperature scales don’t just differ in size; they start at different zero points. That makes them affine rather than proportional, so a single multiplier can’t convert them. We first convert your value to kelvin, the SI scale that starts at absolute zero, then convert from kelvin to the unit you want.
K = °C + 273.15
°F = °C × 9/5 + 32
°C = (°F − 32) × 5/9
Worked example (default inputs)
20 °C = 68 °F
K = °C + 273.15
°F = °C × 9/5 + 32
When to use this converter
Use it for weather forecasts and oven settings from another country, body temperature readings, lab and science work in kelvin, or any recipe that lists temperatures in a scale you don’t use.
Why temperature is different
A Celsius degree is 9/5 the size of a Fahrenheit degree, but water freezes at 0 °C and at 32 °F, so you also have to account for the offset. Doubling a temperature in Celsius does not double it in Fahrenheit. The only point where both scales read the same is −40°. Cooking from a metric recipe? The volume converter turns milliliters into cups.
Absolute zero
Nothing can be colder than absolute zero: 0 K, −273.15 °C or −459.67 °F. If you enter a value below that, the converter shows an error instead of a meaningless result. Kelvin has no degree sign and no negative values.
Worked examples and reference points
Cooking: 350 °F is about 176.7 °C, and 180 °C is exactly 356 °F, so recipes treat the two as the same oven setting. 220 °C is 428 °F, a typical temperature for roasting vegetables or baking bread. The Celsius to Fahrenheit table lists the usual oven settings.
Health: normal body temperature is often quoted as 37 °C, or 98.6 °F, and a fever is usually defined as 38 °C (100.4 °F) or higher. The Fahrenheit to Celsius page includes these values.
Science: room temperature of 25 °C is 298.15 K, water boils at 373.15 K at standard pressure, and liquid nitrogen boils near 77 K (about −196 °C). Use Celsius to kelvin or kelvin to Celsius for lab values.
Temperature differences convert without the offset: a rise of 10 °C is a rise of 18 °F and of 10 K. Use the scale factor 9/5 only, not the +32.
Weather rule of thumb: 0 °C is freezing, 10 °C is cool (50 °F), 20 °C is mild (68 °F) and 30 °C is hot (86 °F). Each 5 °C step is 9 °F.