Temperature Converter
Convert between Celsius, Fahrenheit, Kelvin, Rankine, and Réaumur temperature scales, with every unit updating live as you type — using the correct offset-based conversion formulas, not just a simple multiplier.
Common Temperature Reference Points
- 0°C = 32°F (freezing point of water)
- 100°C = 212°F (boiling point of water)
- 37°C ≈ 98.6°F (average human body temperature)
- 0°C = 273.15 K
- -40°C = -40°F (the point where the scales cross)
- 0 K = -273.15°C (absolute zero)
- 100°C = 80°Ré
Understanding Temperature Scales
Celsius and Fahrenheit both use arbitrary reference points rather than starting at true zero: Celsius sets water's freezing point at 0° and boiling point at 100°, while Fahrenheit — devised by Daniel Gabriel Fahrenheit in the early 1700s using a brine mixture and, later, human body temperature as references — sets those same points at 32° and 212°. Because the two scales don't share a zero, converting between them needs an offset as well as a multiplier: °F = °C × 9/5 + 32, not simply °C × 9/5. Kelvin avoids this problem entirely by starting at absolute zero, making it the standard scale for scientific work where negative temperatures would be physically meaningless.
Absolute zero — 0 K, -273.15°C, -459.67°F — is the coldest temperature theoretically possible, the point at which atomic motion is at its practical minimum, and it's why the Kelvin scale never goes negative. Rankine is an absolute scale like Kelvin but sized in Fahrenheit-sized degrees, used mainly in some US engineering and thermodynamics fields that otherwise work in Fahrenheit. Réaumur, once standard across much of Europe, set water's freezing and boiling points at 0° and 80°; it has been almost entirely replaced by Celsius today, surviving mainly in older texts and some traditional Russian culinary and dairy recipes.
Disclaimer: This converter is provided for general informational and reference purposes only. For applications where precision matters — medical dosing, engineering, construction, or legal and regulatory submissions — verify the result independently or consult a qualified professional.
Frequently Asked Questions
About this calculator
This temperature converter lets you enter a value in any of 5 scales and see it instantly converted to all the others — Celsius, Fahrenheit, Kelvin, Rankine, and Réaumur. Unlike most unit conversions, temperature scales don't share a common zero point, so converting between them requires an offset as well as a multiplier (for example, °F = °C × 9/5 + 32, not just °C × 9/5) — this converter handles that math for you automatically.
- 5 temperature scales at once — Celsius, Fahrenheit, Kelvin, Rankine, and Réaumur, all converted simultaneously as you type.
- Live conversion — Type a value into any scale and every other field updates instantly — no need to click a button or pick a 'from' and 'to' unit.
- Correct offset-based formulas — Applies the true conversion formulas for each scale, including the +32 offset for Fahrenheit and the 273.15 offset for Kelvin, not just a simple ratio.
- Handles negative values and absolute zero — Supports negative temperatures on every applicable scale, and correctly shows 0 K (absolute zero) as -273.15°C and -459.67°F.
- Quick reference table — Common reference points (freezing and boiling water, body temperature, absolute zero) are listed for fast lookup without typing anything.