AnyTool
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How do I convert temperature between Celsius, Fahrenheit and Kelvin?

Type a value into AnyTool Temperature Converter and pick the units. It instantly converts between Celsius, Fahrenheit, Kelvin, Rankine and Réaumur both ways, and shows the value in every scale at once in a copyable table. Everything is calculated in your browser, so nothing is uploaded.

  • Live two-way conversion — type in either field and the other updates
  • Celsius, Fahrenheit, Kelvin, Rankine and Réaumur supported
  • See the value in every scale at once, each row copyable
  • Adjustable decimals with scientific notation for extreme values
  • 100% in your browser — no upload, no signup, works offline

What is

Temperature Conversion

Temperature conversion changes a temperature from one scale to another — for example Celsius to Fahrenheit. Because the scales have different zero points, conversion uses affine formulas (a multiply and an offset) rather than a single factor; for instance degrees Fahrenheit equal degrees Celsius times 9/5 plus 32.

Converters

Related terms

Celsius to FahrenheitKelvinRankineRéaumur

Frequently Asked Questions

Multiply the Celsius value by 9/5 and add 32. So 100 °C is 212 °F.

To convert Celsius to Fahrenheit, multiply by 9/5 (or 1.8) and add 32: °F = °C × 9/5 + 32. For example, 20 °C becomes 68 °F and 100 °C becomes 212 °F. To go the other way, subtract 32 first and then multiply by 5/9.

Add 273.15 to the Celsius value. So 0 °C is 273.15 K.

Kelvin shares the size of the Celsius degree but starts at absolute zero, so you simply add 273.15: K = °C + 273.15. Water freezes at 273.15 K and boils at 373.15 K. To return to Celsius, subtract 273.15 from the Kelvin value.

No. Every calculation runs in your browser, so nothing is sent to a server and it works offline.

AnyTool Temperature Converter computes every result locally in JavaScript using exact conversion formulas through a Kelvin base. No value is uploaded, there is no tracking, and the page keeps working offline after the first load.

Rankine is an absolute scale with Fahrenheit-sized degrees; Réaumur sets water freezing at 0 and boiling at 80.

Rankine starts at absolute zero like Kelvin but uses degrees the size of Fahrenheit, so K = °R × 5/9. The Réaumur scale, once common in Europe, places the freezing point of water at 0 °Ré and the boiling point at 80 °Ré, giving °Ré = °C × 4/5. AnyTool converts both alongside Celsius, Fahrenheit and Kelvin.

Detailed Explanation

Methodology

How the Temperature Converter Works

AnyTool Temperature Converter performs every calculation in the browser. Each scale declares an affine round-trip to a shared Kelvin base — a multiply and an offset — so any unit converts to any other through Kelvin without an N-by-N formula table. Celsius adds 273.15 to reach Kelvin, Fahrenheit uses (°F + 459.67) × 5/9, Rankine uses °R × 5/9, and Réaumur uses °Ré × 5/4 + 273.15. The result is then converted from Kelvin back to the target scale.

  • Five scales: Celsius, Fahrenheit, Kelvin, Rankine and Réaumur
  • Kelvin is the shared base; each scale defines exact to/from formulas
  • Conversion is value to base to value, so any unit maps to any other
  • Editing either field converts both directions live
  • All arithmetic is client-side JavaScript — no server round-trip
How It Works

All Units, Precision and Formulas

A single input is converted into every scale at once in a copyable table, with the source and target rows highlighted. A decimals control sets precision from 0 to 10 places, and magnitudes that are very large or very small automatically switch to scientific notation so results stay readable. A formula reference and a table of common reference points (absolute zero, freezing, body temperature, boiling) accompany the converter.

  • Convert-to-all table shows the value in every scale simultaneously
  • Each unit row is individually copyable
  • Adjustable precision from 0 to 10 decimal places
  • Automatic scientific notation for extreme magnitudes
  • Built-in formula reference and common reference points
Privacy & Security

Privacy and Offline Use

Because all conversion runs in the browser, no value is sent to a server, there is no account or tracking, and the page works offline after first load. The converter is built on a shared, unit-tested conversion engine that other AnyTool unit converters reuse, so behaviour is consistent across the site.

Temperature conversion: in-browser (AnyTool) vs typical online converters
CapabilityAnyToolTypical online converters
ProcessingRuns in your browserOften server-side
ScalesCelsius, Fahrenheit, Kelvin, Rankine, RéaumurOften Celsius/Fahrenheit/Kelvin only
Two-way inputEdit either field, both updateUsually one-direction with a button
All units at onceYes, copyable tableOften one target at a time
Precision controlAdjustable 0-10 decimalsFrequently fixed
Works offlineYes (PWA)No
Cost / signupFree, no signupOften ad-heavy or gated

AnyTool converts every scale locally through a Kelvin base and uploads nothing.