Temperature Converter

Convert between Celsius, Fahrenheit, Kelvin, and Rankine — instantly

°C — Water freezes at 0°C, boils at 100°C
°F — Water freezes at 32°F, boils at 212°F
K — Absolute zero = 0 K. No degree symbol.
°R — Used in some engineering applications

Common Reference Points

Reference Celsius Fahrenheit Kelvin
Absolute zero−273.15°C−459.67°F0 K
Water freezes0°C32°F273.15 K
Room temperature20–22°C68–72°F293–295 K
Body temperature37°C98.6°F310.15 K
Water boils100°C212°F373.15 K

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How to Use the Temperature Converter

  1. Type a value into any of the four fields (Celsius, Fahrenheit, Kelvin, or Rankine).
  2. All other fields update instantly — no button to press.
  3. Results are shown to two decimal places. The reference table shows common real-world temperatures for comparison.
  4. To convert a different value, simply type over the existing number.

What is a Temperature Converter?

A temperature converter translates a temperature reading from one scale to another. The three scales you encounter most often are Celsius (used by most of the world), Fahrenheit (used primarily in the United States), and Kelvin (the SI base unit used in science). A fourth scale, Rankine, is used in some thermodynamic engineering contexts.

Each scale defines temperature relative to different reference points. Celsius and Fahrenheit both define zero based on physical properties of water or brine, while Kelvin starts at absolute zero — the theoretical minimum temperature where atoms have no thermal energy.

Temperature Conversion Formulas

The exact formulas used by this calculator:

  • Celsius to Fahrenheit: °F = (°C × 9/5) + 32
  • Fahrenheit to Celsius: °C = (°F − 32) × 5/9
  • Celsius to Kelvin: K = °C + 273.15
  • Celsius to Rankine: °R = (°C + 273.15) × 9/5

All other conversions are derived from these base formulas using Celsius as the common intermediate.

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Frequently Asked Questions

Multiply by 9, divide by 5, then add 32. The formula is: °F = (°C × 9/5) + 32. For a quick mental estimate, double the Celsius value and add 30 — it won't be exact, but it's close enough for everyday use. For example, 20°C × 2 + 30 = 70°F (exact answer is 68°F).
Subtract 32, then multiply by 5/9. The formula is: °C = (°F − 32) × 5/9. For a quick estimate, subtract 30 and halve the result. For example, 98°F: (98 − 30) ÷ 2 = 34°C (exact answer is 36.7°C). The estimate works well for common temperatures between 0°F and 120°F.
The Celsius and Fahrenheit scales intersect at exactly −40 degrees. That means −40°C = −40°F. You can verify this: (−40 × 9/5) + 32 = −72 + 32 = −40°F. This is an interesting mathematical fact — it's the only temperature where both scales give the same number.
Absolute zero is 0 K (Kelvin), which equals −273.15°C or −459.67°F. It represents the lowest possible temperature — the point at which all atomic thermal motion stops. It is theoretically impossible to reach absolute zero, though scientists have gotten within billionths of a degree of it in laboratory conditions.
The US adopted the Fahrenheit scale in the 18th century before Celsius became the international standard. Fahrenheit was widely used across Europe at the time. When most of the world transitioned to Celsius (as part of metrication in the 19th and 20th centuries), the US did not follow. Today, the US, Myanmar, and Liberia are the only countries that primarily use Fahrenheit.

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