This free online temperature converter instantly converts between Celsius, Fahrenheit, and Kelvin. Enter a temperature, choose your source and target scales, and get an accurate reading for weather, cooking, or science use.
How to Use the Temperature Converter
- Pick the starting scale in the "From Unit" dropdown, such as Celsius (°C) or Fahrenheit (°F).
- Pick the target scale in the "To Unit" dropdown, such as Kelvin (K).
- Enter the temperature you want to convert in the "Value" field.
- Click "Convert" to see the converted temperature immediately.
Temperature cannot be converted with a single multiplication factor the way length or weight can. The three scales put their zero at different points, and a Fahrenheit degree is smaller than a Celsius degree. Each conversion therefore has a scaling step and an offset step. The converter uses these exact formulas:
- Celsius to Fahrenheit: °F = °C × 9/5 + 32
- Fahrenheit to Celsius: °C = (°F − 32) × 5/9
- Celsius to Kelvin: K = °C + 273.15, and Celsius = K − 273.15
- Fahrenheit and Kelvin: the converter goes through Celsius, so K = (°F − 32) × 5/9 + 273.15
Order matters. When going from Fahrenheit to Celsius, subtract 32 first and then multiply by 5/9. Doing it the other way round gives a wrong answer. Results are shown to two decimal places.
Worked Examples
Most digital thermometers sold in India, and many clinics, report body temperature in Fahrenheit, while medical guidance written abroad often uses Celsius. A reading of 101 °F becomes (101 − 32) × 5/9 = 69 × 5/9 ≈ 38.33 °C. A temperature of 100.4 °F, or 38 °C, is the figure commonly used as the threshold for a fever.
Weather reports in India use Celsius. A summer high of 45 °C is 45 × 9/5 + 32 = 81 + 32 = 113 °F, which helps when comparing with forecasts from the US.
Baking recipes from American websites usually give oven temperatures in Fahrenheit. A recipe calling for 350 °F needs about 176.67 °C, so most cooks set an oven marked in Celsius to 175 or 180 °C. Going the other way, 180 °C is exactly 356 °F.
Reference Temperatures
| Celsius | Fahrenheit | Kelvin | What it is |
|---|
| −40 °C | −40 °F | 233.15 K | the point where both scales read the same |
| 0 °C | 32 °F | 273.15 K | water freezes |
| 25 °C | 77 °F | 298.15 K | a comfortable room temperature |
| 37 °C | 98.6 °F | 310.15 K | typical average body temperature |
| 38 °C | 100.4 °F | 311.15 K | commonly treated as the start of a fever |
| 45 °C | 113 °F | 318.15 K | a severe summer heatwave day |
| 100 °C | 212 °F | 373.15 K | water boils at sea level |
| 180 °C | 356 °F | 453.15 K | a common baking temperature |
Common Mistakes
- Converting a temperature change with the full formula. A rise of 5 °C is a rise of 9 °F, not 41 °F. For differences, multiply by 9/5 and leave out the 32.
- Relying on the "double it and add 30" shortcut for anything precise. It works near 10 °C, but at 30 °C it gives 90 °F instead of the correct 86 °F, and the error keeps growing at higher temperatures.
- Writing "degrees Kelvin". Kelvin is written simply as K, without a degree sign, and it never goes below zero because 0 K is absolute zero.
- Assuming a thermometer reading is in Celsius. A reading of 99 on a home thermometer is almost certainly Fahrenheit (about 37.2 °C), since 99 °C would be close to boiling.
Frequently Asked Questions
Multiply the Celsius value by 9/5 and add 32. For example, 0°C equals 32°F, so set "From Unit" to Celsius (°C) and "To Unit" to Fahrenheit (°F) to try it.
0°C equals 273.15 Kelvin, since the Kelvin scale is offset from Celsius by exactly 273.15 degrees with no change in scale size.
It supports Celsius (°C), Fahrenheit (°F), and Kelvin (K), covering the scales most commonly used in weather, cooking, and science.
The textbook figure is 98.6 °F, which is 37 °C. Healthy readings vary from person to person and through the day, and roughly 97 °F to 99 °F (about 36.1 °C to 37.2 °C) is generally considered normal. A reading of 100.4 °F (38 °C) or above is usually treated as a fever.
At −40. Setting °F equal to °C in the formula °F = °C × 9/5 + 32 gives a single solution, −40, so −40 °C and −40 °F are the same temperature.