Temperature Converter

About the Temperature Converter

This converts temperatures between the three common scales — Celsius, Fahrenheit and Kelvin. It's the quick check for a weather forecast in the other scale, an oven or recipe temperature, a scientific value in Kelvin, or a fever reading. Enter a value in any scale and see the others instantly.

How it works — the formulas

Unlike most unit conversions, temperature scales have different zero points, so conversion needs a formula, not just a multiplier:

• Celsius → Fahrenheit: °F = °C × 9⁄5 + 32
• Fahrenheit → Celsius: °C = (°F − 32) × 5⁄9
• Celsius → Kelvin: K = °C + 273.15
• Kelvin → Celsius: °C = K − 273.15

So 0 °C = 32 °F = 273.15 K (water freezes), and 100 °C = 212 °F (water boils at sea level). −40 °C equals −40 °F — the one point where the two scales meet.

Assumptions and behaviour

• Kelvin uses the standard offset of 273.15 from Celsius; absolute zero (0 K) is −273.15 °C.
• The tool accepts negative values (below-freezing temperatures).
• Results are shown to about 7 significant figures.
• Boiling and freezing points quoted are at standard sea-level pressure.

Limitations

• Temperature is not a ratio scale on Celsius or Fahrenheit. 20 °C is not "twice as hot" as 10 °C, because their zero points are arbitrary — only Kelvin has a true zero. So doubling a Celsius or Fahrenheit value is not physically meaningful.
• It doesn't stop you entering temperatures below absolute zero (below −273.15 °C / 0 K), which don't physically exist — the maths still computes them.
• It covers the three everyday scales; it doesn't include Rankine or historical scales like Réaumur.

Privacy

The conversion runs entirely in your browser. Nothing is uploaded or stored.