Four temperature scales, one table
Convert any temperature between Celsius, Fahrenheit, Kelvin and Rankine and see all four scales at once, because you usually need the pair you did not ask for next. The two everyday scales differ in both zero and step, which is why their formulas carry the only addition in this whole conversion section; Kelvin and Rankine fix that by starting at absolute zero, the physically coldest possible temperature, making them the scales of science and engineering thermodynamics respectively.
The formulas
Celsius and Fahrenheit were anchored to water: 0/100 for freezing and boiling against 32/212, so 180 Fahrenheit degrees cover the same span as 100 Celsius degrees — hence the 9/5 ratio — and the zeros sit 32 degrees apart. The famous crossover is −40, identical on both scales, and the quickest sanity check on any conversion. A rough mental rule for weather (double the Celsius and add 30) is fine for deciding on a jacket but drifts by several degrees at the extremes; the table here is exact. Kelvin never uses the degree symbol and never goes negative in reality — enter a value below absolute zero and this tool converts it arithmetically but flags it as physically impossible.
Reference points to calibrate by
Absolute zero is −273.15 °C / −459.67 °F. A healthy body sits near 37 °C / 98.6 °F. Comfortable rooms are 20–22 °C / 68–72 °F. Ovens run 175–230 °C / 350–450 °F. The stats panel labels your temperature with a plain-English feel band so a bare number in an unfamiliar scale still means something. For unit conversions of length and weight, the sibling tools are one click away below.
Worked example
100 °C is 212 °F — the boiling point of water at sea level — and 373.15 K or 671.67 °R on the absolute scales. And −40 °C is −40 °F exactly.
How to use this calculator
- Enter the temperature.
- Choose the scale it is in and the scale you want.
- Read the headline answer and the four-scale table.
- Check the step panel for the formula applied to your number.
Why Fahrenheit feels finer-grained
Between water freezing and boiling, Fahrenheit fits 180 degrees where Celsius fits 100, so one Fahrenheit degree is a smaller step — weather reports in Fahrenheit can sound more precise without decimals. It is also why oven dials in the US jump in 25-degree clicks that look odd in Celsius (350 °F = 176.7 °C, conventionally rounded to 175 or 180 in recipes).
Converting one specific pair? These single-pair pages are pre-set and carry a full table for that pair: Celsius to Fahrenheit and Fahrenheit to Celsius.