Temperature Converter

Whether you are baking a recipe from a European cookbook, studying thermodynamic physics, or planning an international vacation, converting temperature scales accurately is a daily necessity. The Calculay Temperature Converter provides instant, precise translations between Celsius, Fahrenheit, and the absolute Kelvin scale.

The Origins of the Scales

Unlike distance or weight, measuring heat was historically a highly subjective science. Different scientists created different arbitrary baseline points for what "Zero" should mean.

• Fahrenheit (°F): Invented by Daniel Fahrenheit in 1724. He set his zero point based on the freezing temperature of a brine solution made of water, ice, and ammonium chloride. On this scale, pure water freezes at 32°F and boils at 212°F. It is almost exclusively used by the United States.
• Celsius (°C): Invented by Anders Celsius in 1742. It is vastly more logical for everyday life. He set 0°C exactly at the freezing point of water, and 100°C exactly at the boiling point of water. It is the standard scale for 95% of the world.
• Kelvin (K): The ultimate scientific scale. Unlike the other two, Kelvin is an "Absolute" scale. Zero Kelvin (0 K) is Absolute Zero—the theoretical temperature where all atomic movement completely stops. Because it is absolute, it does not use the degree (°) symbol. Water freezes at 273.15 K.

The Mathematics of Conversion

Converting between these scales requires more than just adding or subtracting, because the "size" of a degree is different between Fahrenheit and Celsius. (A change of 1°C is equivalent to a change of 1.8°F).

• Celsius to Fahrenheit: Multiply the Celsius temperature by 1.8 (or 9/5) and then add 32.
• Fahrenheit to Celsius: Subtract 32 from the Fahrenheit temperature, and then divide by 1.8.
• Fun Fact: Due to the math of the linear equations, there is exactly one point where the scales perfectly intersect. -40°C is exactly equal to -40°F.