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Celsius to Fahrenheit Converter

Convert temperatures between Celsius, Fahrenheit, Kelvin, and Rankine in both directions. Rejects values below absolute zero and flags freezing, boiling, and absolute-zero points.

Temperature input
Result
Input: 100 C (Celsius)
Celsius
100 C
Fahrenheit
212 F
Kelvin
373.15 K
Rankine
671.67 R
At or above boiling
Common temperature reference
Absolute zero: -273.15 C / -459.67 F / 0 K
Dry ice sublimation: -78.5 C / -109.3 F / 194.65 K
Water freezing: 0 C / 32 F / 273.15 K
Refrigerator: 4 C / 39.2 F / 277.15 K
Room temperature: 20 C / 68 F / 293.15 K
Body temperature: 37 C / 98.6 F / 310.15 K
Hot summer day: 40 C / 104 F / 313.15 K
Water boiling: 100 C / 212 F / 373.15 K
Pizza oven: 260 C / 500 F / 533.15 K
Lead melting: 327 C / 620.6 F / 600.15 K

Frequently Asked Questions about the Celsius to Fahrenheit Converter

What is the formula to convert Celsius to Fahrenheit?
Multiply the Celsius value by 9/5 and add 32, so F = C x 9/5 + 32. For example, 20 C becomes 20 x 1.8 + 32 = 68 F. To go the other way, subtract 32 first and then multiply by 5/9, so C = (F - 32) x 5/9, which means 68 F becomes (68 - 32) x 5/9 = 20 C.
Why is -40 the same number in Celsius and Fahrenheit?
Setting F equal to C in F = C x 9/5 + 32 gives C = C x 9/5 + 32, then -32 = C x 4/5, so C = -40. That is the one temperature where the two scales cross, and the calculator returns -40 in both units when you enter it in either one.
Why can Kelvin never be negative?
Kelvin is an absolute scale: 0 K is absolute zero, the lowest temperature physically possible (-273.15 C or -459.67 F). Below that, particle motion would have to drop below zero, which is not physical. The converter rejects any Kelvin input below 0 and any Celsius input below -273.15.
What is Rankine and how does it relate to Fahrenheit?
Rankine is the absolute scale built on Fahrenheit-sized degrees, the same way Kelvin sits on Celsius-sized degrees. Zero Rankine is absolute zero (the same point as 0 K), and one Rankine degree equals one Fahrenheit degree. The conversion is Rankine = Fahrenheit + 459.67, and it shows up in US thermodynamics and aerospace engineering.
Which countries still use Fahrenheit?
The United States, the Bahamas, the Cayman Islands, and Belize use Fahrenheit as their default weather and everyday temperature scale. Liberia and Burma (Myanmar) historically used it but have moved over to Celsius, so the practical Fahrenheit zone is now small. Every other country reports weather, cooking, and body temperature in Celsius.

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