Temperature Converter — Celsius, Fahrenheit, Kelvin, Rankine, Réaumur

Instant conversions with adjustable precision. Private by design—everything runs locally in your browser.

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Enter a value in any field; the others update instantly using standard formulas:

  • °F = °C × 9/5 + 32
  • °C = (°F − 32) × 5/9
  • K = °C + 273.15
  • °Ra = K × 9/5 = (°C + 273.15) × 9/5
  • °Ré = °C × 4/5

Both Kelvin and Rankine are absolute scales (start at absolute zero). Kelvin steps match Celsius; Rankine steps match Fahrenheit.

Understanding Temperature Scales

Temperature scales are used to measure the hotness or coldness of an object. While Celsius and Fahrenheit are the most common for everyday use, other scales like Kelvin, Rankine, and Réaumur are vital in scientific and engineering fields.

The Five Scales

  • Celsius (°C): The most widely used scale, with 0°C as the freezing point and 100°C as the boiling point of water.
  • Fahrenheit (°F): Predominantly used in the United States, with 32°F as the freezing point and 212°F as the boiling point of water.
  • Kelvin (K): The standard unit of temperature in science. It is an absolute scale, meaning 0 K is absolute zero, the theoretical point where all molecular motion ceases. There are no degrees in Kelvin.
  • Rankine (°Ra): An absolute scale similar to Kelvin, but based on the Fahrenheit degree. 0°Ra is absolute zero.
  • Réaumur (°Ré): An older scale, primarily used in parts of Europe in the past. Its freezing point is 0°Ré and boiling point is 80°Ré.

Conversion Formulas

The conversion between these scales is based on a set of mathematical formulas, which this calculator uses to provide instant, accurate results. For example:

    • °F = °C × 9/5 + 32
    • °C = (°F − 32) × 5/9
    • K = °C + 273.15
    • °Ra = K × 9/5 = (°C + 273.15) × 9/5
    • °Ré = °C × 4/5

All conversions in this tool are performed client-side using JavaScript, ensuring your privacy and a fast user experience.

Temperature Converter: FAQs

What are the formulas used for conversion?

Examples: °F = °C × 9/5 + 32; K = °C + 273.15; °Ra = (°C + 273.15) × 9/5; °Ré = °C × 4/5.

Is this converter private?

Yes. All calculations run locally in your browser; nothing is uploaded.

What’s the difference between Kelvin and Rankine?

Both start at absolute zero. Kelvin uses Celsius-sized degrees; Rankine uses Fahrenheit-sized degrees.

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