Temperature conversions come up constantly — when travelling, cooking, reading the news, or checking a weather app set to the wrong scale. Here's everything you need to convert between Celsius and Fahrenheit confidently.
The Formula
To convert Celsius to Fahrenheit:
°F = (°C × 9/5) + 32
To convert Fahrenheit to Celsius:
°C = (°F − 32) × 5/9
Quick mental trick: double the Celsius temperature and add 30 for a rough Fahrenheit estimate. For example, 20°C → (20 × 2) + 30 = 70°F (actual answer: 68°F — close enough for everyday use).
Common Temperature Reference Points
| Description | Celsius | Fahrenheit |
|---|---|---|
| Water freezes | 0°C | 32°F |
| Cold winter day | -10°C | 14°F |
| Chilly weather | 10°C | 50°F |
| Mild/comfortable | 20°C | 68°F |
| Warm summer day | 30°C | 86°F |
| Very hot day | 40°C | 104°F |
| Normal body temp | 37°C | 98.6°F |
| Fever | 38.5°C | 101.3°F |
| Oven (baking) | 180°C | 356°F |
| Water boils | 100°C | 212°F |
What About Kelvin?
Kelvin is the scientific standard for temperature measurement. Unlike Celsius and Fahrenheit, it has no negative values — it starts at absolute zero, the coldest possible temperature.
To convert Celsius to Kelvin: K = °C + 273.15
Absolute zero is −273.15°C or −459.67°F. You'll mostly encounter Kelvin in physics, chemistry, and astronomy.
Why Do Two Systems Exist?
Celsius (originally called Centigrade) was developed in the 18th century and is based on water — 0° is freezing, 100° is boiling. It's the standard in almost every country and in all scientific contexts.
Fahrenheit was developed around the same time by Daniel Fahrenheit and is primarily used in the United States today. The scale was originally based on a brine solution's freezing point and human body temperature, which is why the numbers feel less intuitive.
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