What are the temperature scales?
There are four temperature scales in common use. Celsius (°C) is the everyday metric scale — water freezes at 0 and boils at 100. Fahrenheit (°F) is used in the United States for everyday temperatures — water freezes at 32 and boils at 212. Kelvin (K) is the SI base unit of temperature used in physics and chemistry — it starts at absolute zero (−273.15°C), so there are no negative Kelvin values. Rankine (°R) is the Fahrenheit-based absolute scale used in some thermodynamic engineering contexts — absolute zero is 0°R = −459.67°F. Every temperature on one scale maps to a unique value on every other scale.
How to use this tool
- 1 Type a temperature value in the input box at the top.
- 2 Select the input unit from the dropdown: °C, °F, K, or °R.
- 3 All four output cards update instantly with the equivalent value in every scale.
- 4 Click Copy below any output card to copy that value. The Quick Reference table shows common reference points.
Frequently asked questions
What is absolute zero?
Absolute zero is the coldest possible temperature — the point at which atoms have minimum thermal energy. It is 0 K, −273.15°C, −459.67°F, and 0°R. It is a theoretical limit; nothing in the observable universe has been measured at exactly absolute zero.
How do I convert Celsius to Fahrenheit?
Multiply by 9/5 and add 32: °F = (°C × 9/5) + 32. To go the other way: °C = (°F − 32) × 5/9. Body temperature (37°C) is 98.6°F; room temperature (20°C) is 68°F.
What is Rankine used for?
Rankine is used in some US engineering contexts — particularly aerospace and chemical engineering textbooks — where absolute temperature is needed but Fahrenheit units are preferred. It is rarely encountered outside those fields.
Why does the output sometimes show scientific notation?
Very large or very small values are shown in scientific notation (e.g. 1.234e+6) when they exceed four significant figures. This avoids very long decimal strings for extreme temperatures.
Is my data sent anywhere?
No. All conversions run locally using arithmetic formulas in your browser.