Conversions

Temperature Converter

What this does

Convert temperatures exactly between Celsius, Fahrenheit and Kelvin using the official formulas, with absolute-zero validation built in.

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Calculator inputs

How to use it

Using the temperature converter

  1. 01

    Enter the temperature

    Negative values are fine; anything below absolute zero is refused deliberately.

  2. 02

    Choose the scales

    Select Celsius, Fahrenheit or Kelvin for both sides.

  3. 03

    See all three

    The output shows your target scale plus the remaining scale as context.

Good to know

Why −40 is famous

At exactly −40 degrees the two civilian scales agree: (−40 × 9⁄5) + 32 = −40. It is the only crossover point and a handy sanity check whenever a conversion looks suspicious.

Kelvin is not just fancy Celsius

Kelvin starts at absolute zero, making it the natural scale for physics: gas laws and thermal radiation depend directly on absolute temperature. Room temperature near 293 K sounds exotic but is simply 20 °C.

Fever thresholds across scales

Normal body temperature hovers near 37.0 °C / 98.6 °F, and clinicians generally flag readings above 38.0 °C / 100.4 °F. Quick conversion matters when reading advice written for another country’s scale.

How it's calculated

The math behind this calculator

°C = (°F − 32) × 5⁄9 °C = K − 273.15 °F = °C × 9⁄5 + 32 K = °C + 273.15

Unlike other families, temperature scales do not share a zero point, so simple ratios fail. Every conversion routes through Celsius with the exact offset-and-scale formulas above, and any result below absolute zero (−273.15 °C) is rejected as physically impossible.

Assumptions & limitations

  • Results are rounded only for display; full precision is used internally.
  • Conversions use exact standard definitions of each unit.

Worked example

A classic fever check: 100 °F converts to roughly 37.78 °C.

FAQ

Frequently asked questions

Can I enter negative temperatures?
Yes, down to absolute zero. Below −273.15 °C (−459.67 °F, 0 K) the calculator refuses because no colder temperature exists.
Which countries use Fahrenheit?
Principally the United States, its territories and a handful of Caribbean nations; almost everywhere else reports weather in Celsius.
Does wind chill convert?
No; wind chill is an index computed from temperature plus wind speed, not a true temperature. Convert the underlying air temperature instead.

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