Temperature Converter

Celsius, Fahrenheit, and Kelvin: What is the story?

Why do we have different ways to measure temperature? It comes down to what the creators of these scales chose as their reference points.

• Celsius (°C) was created by Anders Celsius in 1742. He built his scale on the simplest properties of water: 0°C is where water freezes, and 100°C is where it boils (at sea level). This base-100 logic makes it extremely practical and the global standard.
• Fahrenheit (°F), created by Daniel Gabriel Fahrenheit in 1724, used a different logic. He set 0°F based on the freezing temperature of a brine solution, and roughly 96°F as human body temperature. This scale is highly precise for air temperature since the difference between hot and cold weather falls neatly within a 0 to 100 scale.
• Kelvin (K)is the thermodynamic temperature scale created by Lord Kelvin in 1848. Unlike the other two, it doesn't use degrees. It starts at absolute zero (0 K)—the absolute coldest theoretical temperature possible, where all molecular motion stops. It is the core scale used in scientific equations and astrophysics.

Formulas for temperature conversion

Converting temperatures is slightly different from other converters because the scales have offset starting points (0°C is 32°F, and 273.15 K).

To convert Celsius to Fahrenheit, you multiply by 9/5 (1.8) and add 32. To convert Fahrenheit back to Celsius, you subtract 32 first, then multiply by 5/9. Since Kelvin scales exactly like Celsius, you only have to add or subtract 273.15 to move between Kelvin and Celsius.

Using the visual thermometer

The interactive thermometer on the right adjusts in real-time as you type, filling with colors that reflect the environmental temperature. Blue represents freezing conditions, green is comfortable room temperature, and orange to red scales up into high heat. It makes visualizing conversions quick and intuitive.