Fahrenheit (1724): Daniel Fahrenheit calibrated to brine (0°F), water freezing (32°F), and body temperature (~96°F). Maps well to human experience: 0°F = very cold, 100°F = very hot.
Celsius (1742): Anders Celsius used two reproducible points: 0°C = water freezes, 100°C = water boils. Used by ~95% of the world.
Kelvin (1848): Lord Kelvin started at absolute zero (-273.15°C = 0K). Used exclusively in physics and chemistry — gas laws, Planck's radiation, quantum mechanics all require Kelvin.
Conversion Formulas
Reference Points
| Event | °C | °F | K |
|---|---|---|---|
| Absolute zero | -273 | -460 | 0 |
| Water freezes | 0 | 32 | 273 |
| Body temperature | 37 | 98.6 | 310 |
| Karachi summer | 40 | 104 | 313 |
| Water boils | 100 | 212 | 373 |
Quick Mental Conversion
Celsius → Fahrenheit rough estimate: (°C × 2) + 30
Example: 25°C → 80°F (actual 77°F — close enough)
Convert precisely with our Temperature Converter.