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Temperature Converter (C, F, K)
Free online temperature converter
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About this tool
About this tool
Temperature Converter converts between Celsius, Fahrenheit, Kelvin, and Rankine using the exact linear formulas of each scale. Enter a value in any unit, select the target scale, and the result appears instantly with a table of all four scales. The conversion runs entirely in your browser with no server contact.
Convert temperatures between the scales used in weather, cooking, science, and engineering. Celsius and Fahrenheit cover daily life, while Kelvin and Rankine serve laboratory and technical work. Type a value, choose the scale, and the tool returns the exact equivalent using the standard conversion formulas.
Built for daily work
- Convert a weather forecast between Celsius and Fahrenheit.
- Translate an oven temperature from a foreign recipe.
- Check a fever reading against the scale your doctor uses.
- Convert laboratory measurements to Kelvin for calculations.
How to use this tool
How to use this tool
Select the scales
Choose the source scale on the left and the target on the right. Swap reverses the direction.
Check the table
The comparison table shows the same temperature in all four scales, useful for double-checking.
Key features
Key features
Four scales
Celsius, Fahrenheit, Kelvin, and Rankine cover weather, cooking, science, and industry.
Exact formulas
Conversions use the precise linear relationships, for example F = C x 9/5 + 32, with no approximation.
Negative values supported
Below-zero temperatures convert correctly, including the famous -40 point where Celsius and Fahrenheit meet.
Instant feedback
Results update with every keystroke, and the four-scale table updates at the same time.
Practical use cases
Practical use cases
- Convert a weather forecast between Celsius and Fahrenheit.
- Translate an oven temperature from a foreign recipe.
- Check a fever reading against the scale your doctor uses.
- Convert laboratory measurements to Kelvin for calculations.
- Compare Rankine and Fahrenheit readings in thermodynamics work.
Private by default
For local tools, input is processed in your browser and is not sent to application analytics.
Data processing noticeTechnical details
Technical details
ProcessingLocal browser processing
ScalesCelsius, Fahrenheit, Kelvin, Rankine
InputFree numeric entry, negatives allowed
FormulasExact linear scale relationships
Limitations and important notes
Limitations and important notes
- Kelvin and Rankine conversions below absolute zero are physically impossible and not shown.
- The tool converts temperature values, not temperature differences like deltas or heat indexes.
- Display rounding is for readability only.
Frequently asked questions
Frequently asked questions
At -40 degrees. Below that point the Fahrenheit number is larger; above it the Celsius number is larger.
Kelvin is an absolute scale that starts at absolute zero, the coldest physically possible temperature. Converting below -273.15 C would produce a physically impossible value.
Rankine is the absolute Fahrenheit-based scale, used mainly in US engineering thermodynamics. Absolute zero is 0 R, and the freezing point of water is 491.67 R.
The formulas are exact; only the displayed decimals are rounded. Precision is preserved internally.
Related guides and solutions
Related guides and solutions
Convert Celsius to Fahrenheit and back
Weather, cooking, and travel all mix Celsius and Fahrenheit. The [temperature converter](tool:temperature-converter) converts between C and F instantly, including Kelvin for scientific work.
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