Temperature Converter
Instantly convert temperatures between Celsius, Fahrenheit, kelvin, Rankine, and four historical scales.
Use a comma or period as the decimal separator; do not use thousands separators.
All scales
Current & technical scales
Historical scales
Good to know
Good to know
The temperature converter converts between Celsius, Fahrenheit, Kelvin, and Rankine as well as the historical Réaumur, Rømer, Delisle, and Newton scales - directly in the browser, with all target values shown at once. Kelvin is displayed correctly without a degree sign, and values below absolute zero are flagged as invalid.
Typical searches include Celsius to Fahrenheit, Kelvin to Celsius, and convert temperature. Calculation runs locally in the browser. The tool converts absolute temperature values; temperature differences (for example, a change of 5 degrees) follow different formulas for scales with an offset and are not covered by this tool.
Typical use cases
Compare all scales at a glance
Enter a value and immediately see the equivalent in Celsius, Fahrenheit, Kelvin, Rankine, and the historical scales - useful when reading older technical literature or international weather data.
Use historical scales for research and literature
Convert values in Réaumur, Rømer, Delisle, or Newton when working with historical sources, old instruments, or texts on the history of science - including a note that the Delisle scale runs in reverse.
Set scientific notation and decimal places
Choose significant digits or scientific notation to present technical calculations, lab records, or simulation data with the right precision.
Tips for better results
Use absolute zero as a sanity check
The calculator flags values below absolute zero (0 K, -273.15 °C) as invalid - a useful signal for spotting typos or the wrong source scale.
Don’t convert differences like absolute values
A change of, say, 10 °C is not simply 10 converted degrees in another scale once that scale has an offset (such as Fahrenheit). For temperature differences, check the appropriate conversion formula separately.
How it works
How it works
Step by step
Features
Features
All scales at once
After entering a value, Celsius, Fahrenheit, Kelvin, Rankine, and the historical scales all appear at once, grouped into current/technical and historical scales.
Physically valid value check
Values below absolute zero are detected and flagged as invalid instead of showing a misleading result.
Adjustable notation and precision
Choose decimal or scientific notation and the number of significant digits to match your use case.
Frequently asked questions
Frequently asked questions
Why is Kelvin shown without a degree sign?
Kelvin is an SI base unit without a degree sign; the correct form is “300 K”, not “300 °K”. The calculator follows this convention.
What does it mean that the Delisle scale runs in reverse?
On the Delisle scale, 0 °De is the boiling point of water, and a higher value means a colder temperature - the opposite of most other scales. The calculator accounts for this automatically.
Can I convert temperature differences?
No, this tool converts absolute temperature values. Differences (for example, “5 degrees warmer”) need a different formula for scales with an offset, such as Fahrenheit, and are not covered by this tool.
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