Temperature Converter
How it works
Three scales in both directions is six conversions, so the converter does not write six formulas. Every reading is turned into Celsius first and back out from there: °C = (°F − 32) × 5/9 one way, °F = °C × 9/5 + 32 the other, and Kelvin is Celsius shifted by 273.15 without changing the size of a degree. Two formulas, each written once, and the three answers cannot disagree with each other.
Absolute zero is treated as a real boundary rather than a tidy-looking limit. Nothing is colder than −273.15 °C, which is −459.67 °F and exactly 0 K, so a reading below it is rejected instead of converted. Exactly absolute zero is fine — it is a temperature, and the coldest one there is.
Frequently asked questions
Why does it show all three scales at once?
Because the second question usually follows the first. An oven at 180 °C is 356 °F, and the same reading is 453.15 K if you need it for a physics answer — showing the row means you never change the target scale and read the page twice.
Why is −300 °C rejected?
Nothing is colder than absolute zero: −273.15 °C, −459.67 °F, 0 K. A temperature below it is not a cold temperature, it is not a temperature, and reporting −26.85 K for it would look like an answer.
How do I convert in my head?
Double the Celsius figure and add 30 for a rough Fahrenheit. The exact formula is °F = °C × 9/5 + 32, and Kelvin is simply °C + 273.15 — the two scales share a degree size, so only the zero point moves.