What this converter does
This tool converts a single temperature value into all four major temperature scales at once: Kelvin (K), Celsius (°C), Fahrenheit (°F) and Rankine (°R). It is a pure physics unit conversion, so it works identically everywhere and is not tied to any country or region. Enter a number, choose the unit it is expressed in, and the converter reports the equivalent reading on every scale.
How to use it
Type the temperature in the Temperature field, then select its unit from the Input unit dropdown (Kelvin, Celsius, Fahrenheit or Rankine). Negative and decimal values are accepted. The converter first translates your input into Celsius as an internal pivot, then derives the other three scales from it.
The formulas explained
The scales are linked by simple linear relations. Celsius and Kelvin share the same degree size and differ only by the 273.15 offset: \(K = C + 273.15\). Fahrenheit scales Celsius by the factor 1.8 (which is 9/5) and adds 32: \(F = 1.8\cdot C + 32\). Rankine is the absolute scale that uses Fahrenheit-sized degrees, so \(R = 1.8\cdot K\), which is also equal to F + 459.67. The offset 459.67 is simply \(273.15 \times 1.8\).
Worked example
Suppose you enter 20 and choose Celsius. The pivot is \(C = 20\). Then $$K = 20 + 273.15 = 293.15 \text{ K},$$ $$F = 1.8 \times 20 + 32 = 68\ ^\circ\text{F},$$ and $$R = 1.8 \times 293.15 = 527.67\ ^\circ\text{R}.$$ So 20 °C equals 293.15 K, 68 °F and 527.67 °R.
FAQ
Why are Celsius and Kelvin steps the same size? Both use the same degree interval; only the zero point differs, so a 1-degree change is identical on both scales.
What is absolute zero in each scale? Absolute zero is \(0 \text{ K} = -273.15\ ^\circ\text{C} = -459.67\ ^\circ\text{F} = 0\ ^\circ\text{R}\). Values below this are physically impossible, and the converter will warn you while still showing the linear result.
What is Rankine used for? Rankine is an absolute scale popular in some engineering and thermodynamics work in the United States, pairing absolute-zero referencing with Fahrenheit-sized degrees.
