Temperature Converter
Convert Celsius to Fahrenheit, Fahrenheit to Celsius, and Kelvin instantly with the exact formula.
This temperature converter switches between Celsius, Fahrenheit, Kelvin and Rankine the moment you type. It is built for the everyday need to translate a weather forecast, an oven setting or a science value — most often Celsius to Fahrenheit and back — using the precise conversion formulas rather than rough rules of thumb.
About the temperature converter
Temperature scales differ in two ways: where they put zero, and how big each degree is. Celsius sets 0° at the freezing point of water and 100° at its boiling point. Fahrenheit puts freezing at 32° and boiling at 212°, so a Fahrenheit degree is smaller and the scales are offset. Kelvin uses the same degree size as Celsius but starts at absolute zero (−273.15 °C), which makes it the SI base unit for temperature used in science.
Because the scales have both an offset and a different step size, temperature cannot be converted with a single multiplier the way length or weight can. Converting Celsius to Fahrenheit uses °F = °C × 9/5 + 32; the reverse is °C = (°F − 32) × 5/9. This tool applies those exact formulas, so a forecast of 25 °C correctly becomes 77 °F, and body temperature of 98.6 °F becomes 37 °C.
How to use this temperature converter
- Type the temperature you want to convert into the value box.
- Select the scale you are converting from (for example, Celsius).
- Select the scale you want the answer in (for example, Fahrenheit).
- The converted temperature appears instantly using the exact formula.
- Use the swap arrows to reverse the scales, or read the grid to see Celsius, Fahrenheit, Kelvin and Rankine together.
Temperature conversion factors
Exact reference factors used by this converter:
Supported temperature units
- °CCelsius
- °FFahrenheit
- KKelvin
- °RRankine
Frequently asked questions
How do I convert Celsius to Fahrenheit?
Multiply the Celsius value by 9/5 (1.8) and add 32. For example, 25 °C × 1.8 + 32 = 77 °F. The converter applies this formula automatically.
How do I convert Fahrenheit to Celsius?
Subtract 32 from the Fahrenheit value, then multiply by 5/9. For example, (98.6 − 32) × 5/9 = 37 °C, which is normal body temperature.
What is the quick way to estimate C to F?
A rough shortcut is to double the Celsius value and add 30 (25 °C → about 80 °F). It is close for everyday temperatures but not exact — use the ×9/5 + 32 formula for accuracy.
What is Kelvin used for?
Kelvin is the SI base unit of temperature used in science. It starts at absolute zero, so there are no negative values. To convert, add 273.15 to a Celsius reading to get Kelvin.
At what temperature are Celsius and Fahrenheit equal?
At −40 degrees. −40 °C equals −40 °F, the single point where the two scales meet, which you can confirm with the converter.