Skip to content
CalcLab

Temperature Converter

Convert between Celsius, Fahrenheit, and Kelvin.
Celsius
Fahrenheit
No data
No results yet — Enter values and run the tool to see results.

What is this converter?

Converts a temperature between Celsius, Fahrenheit, and Kelvin. Unlike every other converter here, temperature scales have different zero points as well as different degree sizes, so the conversion needs an offset as well as a factor.

Use it when:

  • A weather report, oven setting, or specification uses a scale you do not think in.
  • A scientific calculation requires absolute temperature in Kelvin.
  • You want an exact conversion rather than the usual mental approximation.

Intended for: Anyone reading temperatures across scales — cooking, travel, weather, or science.

How is this calculated?

  1. Temperature is not a simple ratio quantity: 20 °C is not "twice as hot" as 10 °C, because 0 °C is an arbitrary reference point rather than an absence of temperature.
  2. The input is therefore first converted to Celsius, which acts as the pivot scale, applying both the scale factor and the offset for the source scale.
  3. That Celsius value is then converted to the target scale, applying that scale's factor and offset.
  4. Kelvin shares its degree size with Celsius but starts at absolute zero, so the conversion between them is a pure offset of 273.15.
  5. Inputs below absolute zero are rejected, since no such temperature exists.

Formulas

Celsius to Fahrenheit

°F = (°C × 9/5) + 32

The 9/5 factor accounts for the smaller Fahrenheit degree; the 32 accounts for the different zero point.

Fahrenheit to Celsius

°C = (°F − 32) × 5/9

Remove the offset first, then rescale the degree size.

Celsius to Kelvin

K = °C + 273.15

Same degree size, different zero — Kelvin starts at absolute zero.

Example

Converting 37 °C (normal human body temperature) to Fahrenheit.

  1. 37 × 9/5 = 66.6.
  2. 66.6 + 32 = 98.6.

Result: 37 °C = 98.6 °F = 310.15 K.

Frequently asked questions

Why does temperature need an offset when other conversions do not?

Because 0 °C and 0 °F do not mean "no temperature" — they are arbitrary reference points. Length, mass, and volume all share a true zero, so a single multiplication suffices for them.

At what temperature do Celsius and Fahrenheit agree?

At −40. Minus forty degrees Celsius is exactly minus forty degrees Fahrenheit.

Why is a temperature below absolute zero rejected?

Absolute zero (−273.15 °C, 0 K) is the lowest physically possible temperature. Accepting a lower value would return an arithmetically valid but physically meaningless result.

Assumptions

What this converter takes as given:

  • Conversion factors are the internationally standardised definitions of each unit, not regional or historical variants.
  • The value you enter is treated as an exact quantity — no measurement uncertainty is carried through the conversion.
  • Results are rounded only for display; the underlying arithmetic uses full precision.
  • Temperatures are absolute readings, not temperature DIFFERENCES — a difference of 10 °C is 18 °F, not 50 °F, because a difference carries no offset.

Limitations

What this converter cannot know or does not model:

  • The converter does not know the precision of your original measurement, so it cannot report significant figures for you.
  • Units that share a name but differ by region or era (for example, different definitions of a gallon or a ton) are offered only in the variants listed in the unit menu.
  • Very large or very small magnitudes are subject to the limits of double-precision floating-point arithmetic.
  • Historic scales such as Rankine, Réaumur, and Delisle are not included.
  • Converting a temperature INTERVAL rather than a reading requires the factor only, without the offset; this converter always applies the offset.

Related tools