The Four Temperature Scales
- Celsius (°C): The international standard. Water freezes at 0°C and boils at 100°C. Used by most of the world.
- Fahrenheit (°F): Used primarily in the USA. Water freezes at 32°F and boils at 212°F.
- Kelvin (K): The SI unit of temperature. Starts at absolute zero (−273.15°C). Used in science and physics.
- Rankine (°R): Like Kelvin but on the Fahrenheit scale. Rarely used today, mainly in some US engineering fields.
Temperature Conversion Formulas
- °C to °F: (°C × 9/5) + 32
- °F to °C: (°F − 32) × 5/9
- °C to K: °C + 273.15
- K to °C: K − 273.15
- °F to K: (°F − 32) × 5/9 + 273.15
Quick Reference: Common Temperature Conversions
- Body temperature: 37°C = 98.6°F
- Room temperature: 22°C = 71.6°F
- Boiling water: 100°C = 212°F = 373.15K
- Freezing water: 0°C = 32°F = 273.15K
- Absolute zero: −273.15°C = −459.67°F = 0K
How to Convert Temperature Online
1Open the Temperature Converter tool.
2Type a value in any field (°C, °F, K, or °R).
3All other fields update instantly — no button needed.
💡 Quick Trick: For a rough Celsius-to-Fahrenheit estimate: double the °C and add 30. So 20°C → about 70°F (actual: 68°F). Good enough for everyday use!
FAQ
At what temperature are Celsius and Fahrenheit equal?
At exactly −40 degrees, both scales are the same: −40°C = −40°F. This is a fun fact worth remembering!