Temperature Converter: Celsius, Fahrenheit, and Kelvin

From checking the morning weather forecast to monitoring precise chemical reactions in a laboratory, measuring thermal energy is a universal necessity. However, different regions and scientific disciplines rely on completely different temperature scales, making quick mental conversions incredibly difficult due to their non-linear baseline offsets.

Our free online Temperature Converter synchronizes all three major scales—Celsius, Fahrenheit, and Kelvin—in real-time. Simply type a value into any of the input fields, and the underlying algorithm will instantly calculate and update the exact equivalent across the other two scales.

Understanding the Three Scales

• Celsius (°C): Developed by Swedish astronomer Anders Celsius in 1742, this metric scale is based entirely on the properties of water. 0 °C is the freezing point of water, and 100 °C is its boiling point at sea level. It is the standard scale used by the majority of the world for daily life.
• Fahrenheit (°F): Created by physicist Daniel Gabriel Fahrenheit in 1724, this imperial scale is primarily used in the United States and its territories. On this scale, water freezes at 32 °F and boils at 212 °F. Because the degrees are "smaller" than Celsius, it allows for more granular temperature reporting without using decimals.
• Kelvin (K): The base unit of temperature in the International System of Units (SI), used exclusively by scientists and engineers. Unlike the others, Kelvin does not use the degree symbol (°). It is an "absolute" scale that starts at Absolute Zero (0 K)—the theoretical point where all atomic movement ceases. 0 K is equivalent to -273.15 °C.

The Conversion Math

Unlike converting distance (where you simply multiply by a ratio), converting temperature requires adjusting for different baseline zero points:

• 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, then divide by 1.8 (or multiply by 5/9).
• Celsius to Kelvin: Simply add 273.15 to the Celsius value.