Temperature Scale Converter
Temperature is reported on several different scales depending on the field, and this converter translates a single value into all four at once. Everyday weather uses Celsius across most of the world and Fahrenheit in the United States, chemistry and physics use the absolute Kelvin scale, and some thermodynamics and engineering work uses Rankine. They are all linked by simple relationships. Fahrenheit is Celsius multiplied by 9/5 with 32 added, so 25 degrees Celsius is 77 degrees Fahrenheit. Kelvin shares the Celsius degree size but starts at absolute zero, so it equals Celsius plus 273.15. Rankine shares the Fahrenheit degree size and also starts at absolute zero, equaling Fahrenheit plus 459.67. Pick the scale you are starting from, enter the value, and the calculator shows the equivalent in the other three scales immediately, so you never have to chain two conversions by hand. The absolute scales, Kelvin and Rankine, never go negative because nothing can be colder than absolute zero, which is 0 Kelvin, minus 273.15 Celsius, minus 459.67 Fahrenheit and 0 Rankine. Every figure is computed deterministically from the formulas shown below, with a worked example that reconciles exactly to the converter defaults so you can trust the numbers for cooking, science or engineering.
From Celsius: F = C x 9/5 + 32, K = C + 273.15, R = F + 459.67. So 25 degrees C is 77.00 degrees F, 298.15 K and 536.67 degrees R.
Temperature conversion formulas
F = C x 9/5 + 32
K = C + 273.15
R = F + 459.67
C = (F - 32) x 5/9
Celsius and Fahrenheit are relative scales; Kelvin and Rankine are absolute scales that start at absolute zero. Kelvin tracks the Celsius degree, Rankine tracks the Fahrenheit degree.
Worked example
Convert 25 degrees Celsius to the other three scales.
- Fahrenheit = 25 x 9/5 + 32 = 45 + 32 = 77.00
- Kelvin = 25 + 273.15 = 298.15
- Rankine = 77 + 459.67 = 536.67
25 degrees Celsius is 77.00 Fahrenheit, 298.15 Kelvin and 536.67 Rankine. These are the converter's default inputs, so the result above matches the widget exactly.
Reference points across scales
Familiar temperatures in all four scales.
| Point | C | F | K |
|---|---|---|---|
| Absolute zero | -273.15 | -459.67 | 0.00 |
| Water freezes | 0.00 | 32.00 | 273.15 |
| Room (default) | 25.00 | 77.00 | 298.15 |
| Water boils | 100.00 | 212.00 | 373.15 |
Weather and temperature reference: US National Oceanic and Atmospheric Administration (NOAA).
Temperature scale converter: frequently asked questions
How do I convert Celsius to Fahrenheit?
Multiply the Celsius value by 9/5, then add 32. For 25 degrees Celsius, 25 times 1.8 is 45, plus 32 gives 77 degrees Fahrenheit. To go the other way, subtract 32 first, then multiply by 5/9. The two scales meet at minus 40, where both read the same.
What are Kelvin and Rankine?
Kelvin and Rankine are absolute temperature scales that start at absolute zero, the point where molecular motion theoretically stops. Kelvin uses the same degree size as Celsius, so Kelvin equals Celsius plus 273.15. Rankine uses the Fahrenheit degree size, so Rankine equals Fahrenheit plus 459.67. Scientists and engineers use absolute scales because they never go negative.
Why does the calculator show all four scales?
Different fields use different scales: everyday weather uses Celsius or Fahrenheit, chemistry and physics use Kelvin, and some thermodynamics and engineering work uses Rankine. Converting a single input into all four at once lets you read a temperature in whatever scale your task requires without a second step.
What is absolute zero in each scale?
Absolute zero is 0 Kelvin, which is minus 273.15 degrees Celsius, minus 459.67 degrees Fahrenheit and 0 degrees Rankine. No temperature can fall below it, which is why the Kelvin and Rankine scales begin there and never take negative values.
What are the temperature formulas?
Fahrenheit equals Celsius times 9/5 plus 32. Kelvin equals Celsius plus 273.15. Rankine equals Fahrenheit plus 459.67, which also equals Kelvin times 9/5. From any one scale you can reach all the others with these relationships.
Official sources
- Weather, temperature and atmospheric reference: US National Oceanic and Atmospheric Administration (NOAA). As at 25 June 2026.
Reviewed by the CalculatorHub team, edited by James Graham, 25 June 2026. See our methodology. This is general information, not financial, tax, legal or investment advice.