Temperature Converter
Free temperature converter: Celsius to Fahrenheit, °F to °C, kelvin and Rankine with the formula shown. Exact fractions, negative values and absolute-zero checks.
How to use Temperature Converter
- 1Type a temperature, including a minus sign for below zero, such as -40 or 98.6.
- 2Select the scale you are converting from and the scale you want.
- 3Check the formula line under the result, or open All units to see every scale at once.
What makes it better
- Celsius, Fahrenheit, Kelvin and Rankine, with Delisle, Newton and Réaumur as extras
- Shows the actual formula for the pair you chose
- Handles negative temperatures and warns below absolute zero
- Exact fractions: 5 °C is exactly 41 °F, and 98.6 °F is exactly 37 °C
About Temperature Converter
Temperature Converter switches between Celsius, Fahrenheit, Kelvin and Rankine, plus the historical Delisle, Newton and Réaumur scales. Temperatures have different zero points, so each conversion uses its own formula, such as °F = °C × 9/5 + 32, worked out with exact fractions. It shows the formula it used and flags values below absolute zero.
Common uses
- Read a US oven recipe in Fahrenheit and set a Celsius oven correctly.
- Convert a weather forecast or body temperature between °C and °F when travelling.
- Switch a physics or chemistry value between Celsius and kelvin in homework.
- Check what the lab freezer setting of -80 °C is in Fahrenheit.
Example
Input
5
Result
5 °C = 41 °F
Good to know
- A temperature and a temperature difference convert differently. A 10 °C rise is a rise of 18 °F, not 50 °F; this page converts temperatures, not differences.
- Values below absolute zero (-273.15 °C, 0 K) are still converted mathematically but marked as physically impossible.
- Delisle, Newton and Réaumur are historical scales, listed for completeness and rarely needed today.
Temperature Converter FAQ
How do I convert Celsius to Fahrenheit?
Multiply the Celsius value by 9/5 (1.8) and add 32. For example 20 °C × 1.8 + 32 = 68 °F. The page applies that formula with exact fractions and prints it under the result.
How do I convert Fahrenheit to Celsius?
Subtract 32 and multiply by 5/9. So 98.6 °F gives (98.6 − 32) × 5/9 = 37 °C. Many Fahrenheit values give a repeating decimal in Celsius, which the page rounds and marks with a ≈ sign.
At what temperature are Celsius and Fahrenheit equal?
At -40. Enter -40 with From °C and To °F and you get -40 °F. It is the one point where both scales read the same number.
What is absolute zero?
Absolute zero is 0 K, which is -273.15 °C or -459.67 °F, the lowest temperature physics allows. If you enter something colder, the page still converts it but shows a warning that it cannot occur in nature.
Is Kelvin written with a degree sign?
No. Kelvin is written as K, without a degree symbol, and one kelvin is the same size as one degree Celsius. The Fahrenheit and Rankine scales do carry the degree sign here (°F, °R).