Convert between Celsius, Fahrenheit, and Kelvin
Temperature scales measure thermal energy in different systems. Celsius (centigrade) is used worldwide for everyday temperatures, Fahrenheit is used in the US, and Kelvin is the scientific absolute scale. Understanding conversions is essential for cooking, weather, science, and international communication.
°F = (°C × 9/5) + 32 | °C = (°F - 32) × 5/9 | K = °C + 273.15
| Calculation | Expression | Result |
|---|---|---|
| Celsius to Fahrenheit | 100°C | 212°F |
| Fahrenheit to Celsius | 98.6°F | 37°C |
| Celsius to Kelvin | 0°C | 273.15 K |
| Freezing point | 32°F | 0°C |
Water freezing: 0°C = 32°F = 273.15K. Water boiling: 100°C = 212°F = 373.15K. Body temperature: 37°C = 98.6°F. Room temperature: ~20-22°C = 68-72°F. Absolute zero: -273.15°C = -459.67°F = 0K.
Fahrenheit was adopted before Celsius was invented and became entrenched. Daniel Fahrenheit's scale (1724) predates Anders Celsius's (1742). Attempts to switch to Celsius in the 1970s largely failed. Fahrenheit's finer gradations (180 degrees between freezing and boiling vs 100) provide more precision for weather without decimals.
Absolute zero (-273.15°C, -459.67°F, 0 K) is the lowest possible temperature where particles have minimum thermal motion. Nothing can be colder. The Kelvin scale starts at absolute zero, making it useful for scientific calculations where negative temperatures would be problematic.
Quick method: Double the Celsius and add 30. Example: 20°C → (20×2)+30 = 70°F (actual: 68°F). More accurate: Multiply by 2, subtract 10%, add 32. This works well for everyday temperatures but less accurately at extremes.
They are the same scale with different names. 'Centigrade' (meaning 100 degrees between freezing and boiling) was renamed to 'Celsius' in 1948 to honor Anders Celsius and avoid confusion with the centigrade (1/100 of a grade) angle measurement.
Fahrenheit and Celsius are equal at -40 degrees. This can be proven: °F = (°C × 1.8) + 32. If °F = °C, then °C = (°C × 1.8) + 32, solving gives °C = -40. This is a useful trivia fact for remembering both scales.