Converting a temperature usually means looking up which formula applies to which pair of scales. Our new Temperature Converter does the lookup for you and shows the result three ways at once.
- Three scales, one input — Celsius, Fahrenheit, and Kelvin, with a swap button to flip the “from” and “to” units instantly.
- The real formulas — F = C × 9/5 + 32 and C = (F − 32) × 5/9 for Celsius↔Fahrenheit, K = C + 273.15 for Celsius↔Kelvin, and Fahrenheit↔Kelvin composed through Celsius as the pivot, exactly the way it’s taught.
- A live reference row — every conversion also shows the same value in all three units at once, so you don’t need to run the converter a second time to see the Kelvin equivalent.
- An honest limit — Kelvin can’t go below zero (that’s absolute zero, −273.15°C), so entering a value that would imply a negative Kelvin reading gets a plain warning instead of a nonsense number.
- Private by default — the conversion is arithmetic that runs entirely in your browser; nothing you type is sent to a server.
Try the famous crossover point: enter −40 as Celsius, convert to Fahrenheit, and watch it come back as exactly −40 — the one temperature where the two scales agree.