Temperature Converter
Temperature is measured on three scales, and each one is the everyday scale somewhere. Celsius is used in most of the world, Fahrenheit is used in the United States, and Kelvin is used in science. A weather forecast might say 25°C or 77°F for the same warm day, an oven recipe might call for 180°C or 350°F, and a science question might ask for the same temperature in Kelvin. Unlike length or weight, temperature cannot be converted by multiplying by one number, because the scales start at different points: 0°C is 32°F, not 0°F. This free temperature converter uses the correct formulas for all three scales, so you get the right answer every time. Type in a value, pick the scale you have and the scale you want, and the result appears at once, along with the same temperature in all three scales in the table below. There is nothing to install and nothing to sign up for, and every conversion runs entirely in your browser.
Convert Temperature
Your Temperature Conversion
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How to Use This Converter
- Enter your value in the first box. The converter starts with 100, but you can type any number, including decimals and negatives such as -40 or 37.5.
- Choose the scale you have from the From dropdown — Celsius, Fahrenheit, or Kelvin. This is the scale your temperature is currently in.
- Choose the scale you want from the To dropdown. The result updates instantly, every time you type or change either dropdown, with no button to press.
- Read the big result, then check the full table to see the same temperature in all three scales at once. If you need the reverse conversion, tap Swap Units and the two scales trade places.
Worked Example
100°C = 212°F = 373.15 K. Water boils at 100°C at sea level. To get Fahrenheit, multiply by 9/5 and add 32: 100 × 9/5 = 180, and 180 + 32 = 212°F. To get Kelvin, add 273.15: 100 + 273.15 = 373.15 K. All three numbers describe exactly the same temperature.
0°C = 32°F = 273.15 K. Water freezes at 0°C at sea level. In Fahrenheit that is 0 × 9/5 + 32 = 32°F, and in Kelvin it is 0 + 273.15 = 273.15 K. Freezing and boiling are the two anchors of the Celsius scale, 100 degrees apart, while the same two points are 180 degrees apart on the Fahrenheit scale — which is why one Celsius degree is bigger than one Fahrenheit degree.
-40°C = -40°F. Minus 40 is the one temperature where Celsius and Fahrenheit meet. Check it with the formula: -40 × 9/5 = -72, and -72 + 32 = -40°F. In Kelvin that is -40 + 273.15 = 233.15 K. A few more landmarks help you judge any answer: normal body temperature is 37°C, which is 98.6°F and 310.15 K, and a comfortable room is about 20°C, which is 68°F and 293.15 K. If your converted weather temperature comes out near one of these landmarks, you know at a glance whether it is freezing, mild, warm, or hot.
Tips for Accurate Temperature Conversions
The most common temperature mistake is forgetting the +32 when converting to Fahrenheit, or forgetting to subtract it when converting back. Multiplying by 9/5 alone is not enough: 100°C is not 180°F, it is 212°F, because the Fahrenheit scale starts 32 degrees above the Celsius zero. The second most common mistake is applying the same idea to Kelvin, which needs no multiplication at all — Kelvin and Celsius degrees are the same size, so you only add or subtract 273.15.
Remember the direction of each formula: Fahrenheit = Celsius × 9/5 + 32, Celsius = (Fahrenheit − 32) × 5/9, and Kelvin = Celsius + 273.15. For rough estimates, doubling the Celsius number and adding 30 gets you close to Fahrenheit — 20°C is roughly 70°F by that trick, against the exact 68°F — but use the converter for cooking, science, and health, where a few degrees matter. Also note that Kelvin has no negative values and no degree symbol: it is written as 273.15 K, not 273.15°K, because it measures from absolute zero, the coldest temperature possible. Finally, when a recipe or a weather report gives a temperature range, convert both ends of the range separately rather than converting the middle and guessing the rest, because the gap between the ends changes size between scales.
Frequently Asked Questions
What is 100 degrees Celsius in Fahrenheit?
100°C = 212°F = 373.15 K. Water boils at 100°C at sea level, which is 212°F. Multiply 100 by 9/5 to get 180, then add 32 to get 212°F. Add 273.15 to 100 to get 373.15 K.
What is 0 degrees Celsius in Fahrenheit and Kelvin?
0°C = 32°F = 273.15 K. Water freezes at 0°C at sea level, which is 32°F. Add 273.15 to 0 to get 273.15 K. These two points, freezing and boiling, are the anchors of the Celsius scale.
At what temperature are Celsius and Fahrenheit equal?
-40°C = -40°F. Minus 40 is the one temperature where the two scales meet, so -40 degrees means the same thing in Celsius and in Fahrenheit. It is a useful check: if your conversion gives -40 on both scales, the maths is right.
How do I convert Fahrenheit to Celsius?
Subtract 32 from the Fahrenheit temperature, then multiply by 5/9. For example, 68°F minus 32 is 36, and 36 x 5/9 = 20°C. To go the other way, multiply the Celsius temperature by 9/5 and add 32.
What is 0 Kelvin?
0 Kelvin is absolute zero, the lowest temperature possible, equal to -273.15°C and -459.67°F. The Kelvin scale starts at absolute zero and has no negative values, which is why scientists use it. Room temperature, about 20°C, is 293.15 K.