Temperature converter
Convert between Celsius, Fahrenheit, and Kelvin, instantly and entirely in your browser. Nothing is uploaded.
The amount to convert. Leave empty or non-numeric for no result.
Three scales, one exact transform
Celsius, Fahrenheit, and Kelvin do not share a zero point, so converting between them is more than a multiply — it is a scale and a shift. This tool applies the exact relationships (°F = °C × 9/5 + 32 and K = °C + 273.15) so freezing, body temperature, and boiling all line up across the three scales. Pick any two and convert in either direction.
Runs entirely on your device
There is no server, no account, and no upload. The math is a few lines of JavaScript that execute in your browser, so the tool works offline and your figures stay private, whether you are reading a recipe, a weather report, or a lab measurement.
Frequently asked questions
- Does this send my data anywhere?
- No. The converter is plain JavaScript that runs entirely in your browser. There is no upload, no network request, and no account. The numbers you type never leave your device.
- How do I convert Celsius to Fahrenheit?
- Multiply by 9/5 and add 32: °F = °C × 9/5 + 32. So 0°C is 32°F and 100°C is 212°F. The converter does this for you in either direction, and also handles Kelvin.
- How does Kelvin relate to Celsius?
- Kelvin uses the same degree size as Celsius but starts at absolute zero, so K = °C + 273.15. That means 0°C is 273.15 K and 100 K is −173.15°C.
- Why is temperature different from other converters?
- Temperature scales do not share a zero point — 0°C, 0°F, and 0 K are three different temperatures — so a conversion is not a simple multiply. It is an affine transform (scale and shift), which this tool applies exactly using each scale's offset from Kelvin.
- How precise are the results?
- Conversions use the exact scale definitions, so results are accurate within floating-point limits. Long fractional results are rounded to twelve significant figures for readability.