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Temperature Converter
Convert between Celsius, Fahrenheit, Kelvin, and Rankine instantly. Click any result to use it as the new input.
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🌡️ Enter Temperature
Common Reference Temperatures
💡 Quick Facts
-40° — the only point where °C equals °F
0 K — absolute zero, the coldest possible temperature
Rankine — used in US engineering; 0°R = 0 K
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Enter a temperature value above
All four unit conversions will appear here instantly
Converting…
In perspective
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Conversion Formulas from
Common Reference Points
Reference
°C
°F
K
°R
The four scales and the conversion chain
All four scales are linear, so each conversion is a multiply and an add. Celsius and Kelvin share the same degree size and differ only by an offset of 273.15, the point of absolute zero. Fahrenheit and Rankine likewise share a degree size and differ by an offset of 459.67. A Celsius degree is 1.8 times the size of a Fahrenheit degree, which is where the 9/5 and 5/9 factors come from.
From Celsius the formulas are: Fahrenheit equals Celsius times 9/5 plus 32; Kelvin equals Celsius plus 273.15; Rankine equals Celsius plus 273.15, times 9/5.
From Fahrenheit: Celsius equals Fahrenheit minus 32, times 5/9; Kelvin equals Fahrenheit minus 32, times 5/9, plus 273.15; Rankine equals Fahrenheit plus 459.67.
From Kelvin: Celsius equals Kelvin minus 273.15; Fahrenheit equals Kelvin minus 273.15, times 9/5, plus 32; Rankine equals Kelvin times 9/5.
From Rankine: Fahrenheit equals Rankine minus 459.67; Celsius equals Rankine minus 491.67, times 5/9; Kelvin equals Rankine times 5/9. The tool converts your input to Celsius internally, then out to each target.
From Celsius the formulas are: Fahrenheit equals Celsius times 9/5 plus 32; Kelvin equals Celsius plus 273.15; Rankine equals Celsius plus 273.15, times 9/5.
From Fahrenheit: Celsius equals Fahrenheit minus 32, times 5/9; Kelvin equals Fahrenheit minus 32, times 5/9, plus 273.15; Rankine equals Fahrenheit plus 459.67.
From Kelvin: Celsius equals Kelvin minus 273.15; Fahrenheit equals Kelvin minus 273.15, times 9/5, plus 32; Rankine equals Kelvin times 9/5.
From Rankine: Fahrenheit equals Rankine minus 459.67; Celsius equals Rankine minus 491.67, times 5/9; Kelvin equals Rankine times 5/9. The tool converts your input to Celsius internally, then out to each target.
Converting 100 degrees Fahrenheit into every scale
Enter 100 and set the source unit to Fahrenheit.
Celsius: subtract 32 to get 68, then multiply by 5/9. 68 times 5 is 340, divided by 9 is 37.78, so 37.78 degrees Celsius.
Kelvin: add 273.15 to the Celsius figure. 37.78 plus 273.15 is 310.93 K.
Rankine: add 459.67 to the Fahrenheit figure directly. 100 plus 459.67 is 559.67 degrees Rankine. You can check this against the Kelvin result, since Rankine equals Kelvin times 1.8: 310.93 times 1.8 is 559.67, which matches.
The result cards also note that 37.78 Celsius sits just above normal human body temperature of 37 Celsius, which is 98.6 Fahrenheit.
For a second check, press the minus 40 preset. Because the two scales cross at that point, the display reads minus 40 Celsius and minus 40 Fahrenheit, with 233.15 K and 419.67 degrees Rankine. Any input below minus 273.15 Celsius is flagged, as it falls below absolute zero.
Celsius: subtract 32 to get 68, then multiply by 5/9. 68 times 5 is 340, divided by 9 is 37.78, so 37.78 degrees Celsius.
Kelvin: add 273.15 to the Celsius figure. 37.78 plus 273.15 is 310.93 K.
Rankine: add 459.67 to the Fahrenheit figure directly. 100 plus 459.67 is 559.67 degrees Rankine. You can check this against the Kelvin result, since Rankine equals Kelvin times 1.8: 310.93 times 1.8 is 559.67, which matches.
The result cards also note that 37.78 Celsius sits just above normal human body temperature of 37 Celsius, which is 98.6 Fahrenheit.
For a second check, press the minus 40 preset. Because the two scales cross at that point, the display reads minus 40 Celsius and minus 40 Fahrenheit, with 233.15 K and 419.67 degrees Rankine. Any input below minus 273.15 Celsius is flagged, as it falls below absolute zero.
Rounding, absolute zero and the mistakes people make
Two conversions are often confused: temperature values versus temperature differences. Converting a reading of 20 degrees Celsius to Fahrenheit uses the full formula with the plus 32 offset, giving 68. But converting a temperature change of 20 Celsius degrees uses only the ratio, giving 36 Fahrenheit degrees, because an offset does not apply to a difference. Use this tool for readings, not for deltas.
Rounding matters in cooking and lab work. Oven conversions are usually rounded to the nearest 5 or 10 degrees in recipes, so a recipe's 180 Celsius and 350 Fahrenheit are conventional equivalents rather than exact ones; the exact conversion of 350 Fahrenheit is 176.67 Celsius. The tool shows a rounded display value with the exact figure beneath it when the two differ.
Kelvin and Rankine are absolute scales, so they have no degree sign in the Kelvin case and cannot go below zero. Absolute zero is minus 273.15 Celsius, minus 459.67 Fahrenheit, 0 K and 0 degrees Rankine. Values below that point are physically meaningless and the tool marks them accordingly.
Rounding matters in cooking and lab work. Oven conversions are usually rounded to the nearest 5 or 10 degrees in recipes, so a recipe's 180 Celsius and 350 Fahrenheit are conventional equivalents rather than exact ones; the exact conversion of 350 Fahrenheit is 176.67 Celsius. The tool shows a rounded display value with the exact figure beneath it when the two differ.
Kelvin and Rankine are absolute scales, so they have no degree sign in the Kelvin case and cannot go below zero. Absolute zero is minus 273.15 Celsius, minus 459.67 Fahrenheit, 0 K and 0 degrees Rankine. Values below that point are physically meaningless and the tool marks them accordingly.
Frequently Asked Questions
Multiply the Celsius value by 9/5, which is 1.8, then add 32. For example 25 Celsius becomes 25 times 1.8, which is 45, plus 32, giving 77 Fahrenheit. To reverse it, subtract 32 first and then multiply by 5/9, so 77 Fahrenheit returns to 25 Celsius.
Rankine is the absolute scale that pairs with Fahrenheit, used in thermodynamics and engineering in the United States. It starts at absolute zero like Kelvin but uses Fahrenheit-sized degrees, so Rankine equals Fahrenheit plus 459.67, and also equals Kelvin multiplied by 1.8.
At minus 40 degrees. It is the single point where the two scales cross, so minus 40 Celsius equals minus 40 Fahrenheit exactly. There is a preset button for it. In Kelvin that point is 233.15 K, and in Rankine it is 419.67 degrees.
You can type it, but the tool flags it. Absolute zero is minus 273.15 Celsius, minus 459.67 Fahrenheit, 0 Kelvin and 0 Rankine, and nothing can be colder. If you see such a result, check whether you selected the correct source unit before converting.
Recipes round oven temperatures to convenient marks. The exact conversion of 350 Fahrenheit is 176.67 Celsius, which recipe writers round to 180 because ovens are set in increments and are rarely accurate to a fraction of a degree. Either setting works for baking.