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Convert temperatures between Celsius, Fahrenheit, and Kelvin with our free online temperature converter. Real-time bidirectional conversion with common reference points.
| °C | °F | K | |
|---|---|---|---|
| Absolute Zero | -273.15 | -459.67 | 0 |
| Water Freezing Point | 0 | 32 | 273.15 |
| Room Temperature | 20 | 68 | 293.15 |
| Human Body Temperature | 37 | 98.6 | 310.15 |
| Water Boiling Point | 100 | 212 | 373.15 |
This temperature converter provides accurate conversions based on standard temperature scale relationships. Results are rounded to 2 decimal places for practical use.
The formulas used are the internationally accepted standard conversions between Celsius, Fahrenheit, and Kelvin temperature scales.
Temperature conversion is the process of changing a temperature value from one measurement scale to another. The three most commonly used temperature scales are Celsius (used in most countries), Fahrenheit (used primarily in the United States), and Kelvin (used in scientific contexts). Each scale has its own zero point and degree size, making conversion necessary when working across different systems or regions.
°F = (°C × 9/5) + 32Multiply the Celsius temperature by 9/5 (or 1.8), then add 32 to get the Fahrenheit equivalent.
°C = (°F - 32) × 5/9Subtract 32 from the Fahrenheit temperature, then multiply by 5/9 (or divide by 1.8) to get the Celsius equivalent.
K = °C + 273.15Add 273.15 to the Celsius temperature to get the Kelvin equivalent. Kelvin uses the same degree size as Celsius but starts at absolute zero.
The Celsius scale, also known as centigrade, sets 0° at the freezing point of water and 100° at the boiling point at standard atmospheric pressure. It was developed by Swedish astronomer Anders Celsius in 1742.
Common usage: Most countries worldwide, scientific research, weather reports outside the US
The Fahrenheit scale sets 32° at the freezing point of water and 212° at the boiling point. It was proposed by German physicist Daniel Gabriel Fahrenheit in 1724.
Common usage: United States, Bahamas, Cayman Islands, Liberia, Palau, and some Caribbean nations
The Kelvin scale is an absolute thermodynamic temperature scale that starts at absolute zero (-273.15°C), the point where all molecular motion stops. It does not use degrees and is named after Lord Kelvin.
Common usage: Scientific research, physics, chemistry, engineering, and astronomy
To convert Celsius to Fahrenheit, multiply the Celsius temperature by 9/5 (or 1.8) and then add 32. The formula is: °F = (°C × 9/5) + 32. For example, 25°C = (25 × 1.8) + 32 = 77°F.
The United States adopted the Fahrenheit scale in its early history when it was the most common temperature scale used in English-speaking countries. Despite most countries later switching to Celsius as part of metric system adoption, the US has maintained Fahrenheit for everyday use due to cultural inertia and the cost of transitioning.
Absolute zero is -273.15°C (-459.67°F or 0 K), the lowest theoretically possible temperature. At this point, atoms would have minimum thermal motion. It's impossible to reach because the laws of thermodynamics prevent complete removal of thermal energy from a system.
Kelvin is preferred in science because it's an absolute scale starting at absolute zero, making it ideal for thermodynamic calculations. Many physics equations require temperatures in Kelvin to work correctly. Also, Kelvin avoids negative numbers, which simplifies many calculations.
Celsius and Centigrade refer to the same temperature scale. The name 'Centigrade' was used historically, but in 1948, the 9th General Conference on Weights and Measures renamed it to 'Celsius' in honor of Anders Celsius. Both names are still used interchangeably in everyday language.
Celsius and Fahrenheit are equal at -40 degrees. This is the only point where both scales intersect. You can verify this: (-40 × 9/5) + 32 = -72 + 32 = -40°F.
Normal room temperature is typically defined as 20-22°C, which equals 68-72°F or 293-295 K. However, comfort levels vary by individual, and different contexts may use slightly different definitions.
For a quick estimate, double the Celsius value and add 30. This gives an approximate Fahrenheit value that's accurate within a few degrees for typical weather temperatures. For example, 20°C × 2 + 30 = 70°F (actual: 68°F).