Guide
Celsius vs Fahrenheit: A Complete Guide
Understand Celsius and Fahrenheit scales, common reference points, conversion formulas, and when each scale is used around the world.
5 min read
Why two temperature scales?
Celsius (°C) is based on the freezing and boiling points of water at sea level: 0°C and 100°C. It is used in most countries for weather, cooking, and daily life.
Fahrenheit (°F) sets water freezing at 32°F and boiling at 212°F. It is the standard in the United States for weather forecasts, oven settings, and medical thermometers.
Reference points to remember
These anchors help you sanity-check any conversion:
- Water freezes: 0°C = 32°F
- Room temperature: about 20°C = 68°F
- Body temperature: about 37°C = 98.6°F
- Water boils: 100°C = 212°F
- Hot summer day: 30°C = 86°F
- Cold winter day: 0°F ≈ −18°C
Conversion formulas
To convert Celsius to Fahrenheit: °F = (°C × 9/5) + 32. Example: 25°C → (25 × 1.8) + 32 = 77°F.
To convert Fahrenheit to Celsius: °C = (°F − 32) × 5/9. Example: 350°F (common baking temp) → (350 − 32) × 5/9 ≈ 177°C.
Kelvin is used in science. K = °C + 273.15. Absolute zero is 0 K (−273.15°C). You will rarely see Kelvin in weather apps, but it appears in physics and chemistry.
Practical tips
Oven recipes from the US list Fahrenheit; European recipes use Celsius. Always convert before adjusting temperature — a 20-degree mistake can ruin a bake.
Weather apps let you switch units in settings. When traveling, learn a few anchors (0°C/32°F, 20°C/68°F) so you can dress appropriately without pulling out a phone.