Celsius to Fahrenheit Guide: Temperature Conversion Explained

Last updated: November 2025 | 8 min read

Understanding temperature conversion between Celsius and Fahrenheit is essential for travel, cooking, and understanding weather reports from different countries. This guide explains the formulas, provides handy charts, and offers tips for quick mental conversions.

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The Conversion Formulas

Celsius to Fahrenheit: °F = (°C × 9/5) + 32

Fahrenheit to Celsius: °C = (°F - 32) × 5/9

Quick Reference Chart

CelsiusFahrenheitDescription
-40°C-40°FWhere scales meet
-18°C0°FVery cold
0°C32°FFreezing point of water
10°C50°FCool weather
20°C68°FRoom temperature
25°C77°FWarm day
30°C86°FHot day
37°C98.6°FBody temperature
100°C212°FBoiling point of water

Mental Math Tricks

Quick Celsius to Fahrenheit

Double the Celsius, subtract 10%, add 32:

  • 20°C: (20 × 2) = 40, minus 4 = 36, plus 32 = 68°F
  • Or simply: Double it and add 30 for a rough estimate

Common Uses in the UK

The UK officially uses Celsius, but Fahrenheit still appears in some contexts:

Cooking Temperatures

DescriptionCelsiusFahrenheitGas Mark
Very low110°C225°F¼
Low140°C275°F1
Moderate180°C350°F4
Moderately hot200°C400°F6
Hot220°C425°F7
Very hot240°C475°F9

Why Two Different Scales?

Fahrenheit was developed by Daniel Fahrenheit in 1724, using a mixture of ice, water, and salt as 0°F and human body temperature as roughly 100°F. Celsius, developed by Anders Celsius in 1742, uses water's freezing point (0°C) and boiling point (100°C) as reference points.

Most of the world uses Celsius, while the United States primarily uses Fahrenheit. The UK switched to Celsius in the 1960s but retains some Fahrenheit usage.

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