Type one temperature and see it on five scales at once: Celsius, Fahrenheit, Kelvin, Rankine and Reaumur, with impossible readings refused in plain words.
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This temperature converter takes one value and shows it on five scales at the same time: Celsius, Fahrenheit, Kelvin, Rankine and Reaumur. Type a temperature, pick the scale it is in, and the other four fill in beside it, worked out with the proper formulas rather than a rough rule of thumb.
One number in, five scales out.
Length and weight scales all start at the same zero, so a single multiplying factor moves between them. Temperature scales do not. Zero Celsius is the freezing point of water, zero Fahrenheit sits well below it, and zero Kelvin is absolute zero, the coldest point there is.
That is why the conversions carry offsets. Fahrenheit is Celsius times 9/5 plus 32, and Kelvin is Celsius plus 273.15. A factor alone would put freezing water at the wrong place on every scale.
Weather reports make the difference vivid. A forecast of 30 degrees is a hot day in Celsius and a freezing one in Fahrenheit, and travellers mix the two up every winter. Seeing both figures side by side, from one typed number, kills that confusion on the spot.
The five scales each have their home ground. Celsius and Fahrenheit run daily life in different countries, Kelvin runs science, Rankine shows up in American engineering, and Reaumur survives in a few European food and drink traditions.
Three anchors settle most arguments. Water freezes at 0 degrees Celsius and 32 degrees Fahrenheit, it boils at 100 and 212, and a healthy body sits near 37 degrees Celsius. If a conversion lands far from the anchor you expected, the scale pick is the first thing to check.
One curiosity is worth knowing: minus 40 is the only temperature where Celsius and Fahrenheit read the same number. Below that point the two scales swap which one gives the bigger figure, a common source of confusion in cold-weather reports.
There is also a hard floor. Nothing in the universe sits below absolute zero, so a conversion that lands under it is refused here with a plain explanation instead of a printed number. A fake reading below that floor would be a made-up answer.
Kelvin follows its own writing rule: it takes no degree symbol and no word “degrees”. A lab temperature is written as 300 K, plain. The other four scales keep their degree wording as usual.
The tool runs fully in your browser. Your figures are never uploaded or stored, you need no account, and conversions are unlimited.
Multiply the Celsius figure by 9/5 and add 32. So 20 degrees Celsius becomes 68 degrees Fahrenheit. The tool does it for all five scales at once, so you never run the formula by hand.
The same. Minus 40 is the single crossover point where both scales agree. Type it in either scale and the other reads minus 40 back at you.
Because it landed below absolute zero, which is 0 Kelvin, or minus 273.15 degrees Celsius. No real temperature exists under that floor, so the tool explains the problem instead of inventing a reading.
Kelvin is an absolute scale counted from zero itself, and by convention it is written as a plain number with a K: 300 K, not 300 degrees. The tool follows that convention in its results.
Rankine is an absolute scale built on Fahrenheit-sized degrees, so its zero is absolute zero too. It appears in some American engineering work, in fields like aerospace and thermodynamics.
Mostly in a few European food traditions, including some cheese making and older confectionery, and in historical records. It is here so old recipes and documents still convert cleanly.
Same rules as this one: free, in your browser, with nothing uploaded.
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