⚖️ Comparison · Updated for 2026
Celsius vs Fahrenheit
Side-by-side comparison, when-to-use-each guide, and instant conversion. Reviewed for 2026.
Quick answer: °F = (°C × 9/5) + 32. °C = (°F − 32) × 5/9. The scales meet at -40° (-40°C = -40°F). 0°C = 32°F (water freezes); 100°C = 212°F (water boils at sea level).
Decision guide — when to use which
Use Celsius when…
Most of the world. UK weather and recipes. Scientific work (alongside Kelvin).
Use Fahrenheit when…
United States, Bahamas, Belize, Cayman Islands, Palau. Some older UK ovens still show Fahrenheit alongside Celsius.
📊 Side-by-side comparison
| Aspect | Celsius | Fahrenheit |
|---|---|---|
| Freezing point of water | 0°C | 32°F |
| Boiling point of water | 100°C | 212°F |
| Normal body temperature | 37°C | 98.6°F |
| Comfortable room | 20-22°C | 68-72°F |
| Origin | Anders Celsius, 1742 | Daniel Fahrenheit, 1724 |
Frequently asked
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What's the easy mental conversion?
For °C to °F: double the Celsius, subtract 10%, add 32. (E.g. 20°C × 2 = 40, − 4 = 36, + 32 = 68°F.) For °F to °C: subtract 30, halve. Not exact but within 3°C for everyday weather.
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Why is normal body temp 98.6°F?
It's a rounded conversion of 37°C. The 'official' 98.6°F is misleadingly precise — actual normal body temp varies by 1°F throughout the day, by individual, and by measurement method.
Reviewed for 2026. All conversion factors and historical references verified against official sources (ISO standards, government weights & measures legislation, IEC technical specifications). Built by a UK-based qualified primary teacher and FA Level 2 coach as part of 247QuickTools' free utility-tools project. We don't sell SEO links or accept paid placements in this content.