Quick example
Convert 20 degrees Celsius to Fahrenheit
Multiply 20 by 9/5 to get 36, then add 32. The result is 68 degrees Fahrenheit. On the absolute scales, the same temperature is 293.15 kelvin or 527.67 degrees Rankine.
Quick reference
Common temperature conversions
| Reference point | Celsius | Fahrenheit | Kelvin |
|---|---|---|---|
| Absolute zero | −273.15 °C | −459.67 °F | 0 K |
| Celsius/Fahrenheit equal | −40 °C | −40 °F | 233.15 K |
| Water freezes | 0 °C | 32 °F | 273.15 K |
| Room temperature | 20 °C | 68 °F | 293.15 K |
| Average body temperature | 37 °C | 98.6 °F | 310.15 K |
| Water boils | 100 °C | 212 °F | 373.15 K |
Freezing and boiling values assume pure water at standard atmospheric pressure; actual boiling temperature changes with pressure and altitude.
Temperature scales
How the four scales relate
Celsius
Water freezes at 0 °C and boils near 100 °C at standard atmospheric pressure.
Fahrenheit
Water freezes at 32 °F and boils near 212 °F. One Fahrenheit degree is 5/9 the size of one Celsius degree.
Kelvin
Kelvin begins at absolute zero. One kelvin is the same interval as one Celsius degree, and kelvin values do not use a degree symbol.
Rankine
Rankine also begins at absolute zero but uses Fahrenheit-sized increments. One kelvin equals 1.8 degrees Rankine.
Physical boundary
Nothing goes below absolute zero
Absolute zero is 0 K, 0 °R, −273.15 °C, or −459.67 °F. The calculator accepts negative Celsius and Fahrenheit values but reports an error when an input falls below the absolute-zero limit for its selected scale. Displayed results use up to 12 significant digits.
Common questions
Temperature conversion FAQ
How do I convert Celsius to Fahrenheit?
Multiply Celsius by 9/5, then add 32. For example, 20 °C equals 68 °F.
How do I convert Fahrenheit to Celsius?
Subtract 32 from Fahrenheit, then multiply by 5/9. For example, 68 °F equals 20 °C.
At what temperature are Celsius and Fahrenheit equal?
Both scales have the same numerical value at −40 degrees.
What is absolute zero?
Absolute zero is 0 K, −273.15 °C, −459.67 °F, or 0 °R.
What is the difference between Kelvin and Rankine?
Both begin at absolute zero. Kelvin uses Celsius-sized increments; Rankine uses Fahrenheit-sized increments.