Celsius to Fahrenheit: Conversion Formula Explained

The Celsius to Fahrenheit formula

The formula to convert Celsius (°C) to Fahrenheit (°F) is:

°F = (°C × 9/5) + 32

Or equivalently:

°F = (°C × 1.8) + 32

Step-by-step example

Convert 25°C to Fahrenheit:

1. Multiply by 9/5: 25 × 1.8 = 45
2. Add 32: 45 + 32 = 77°F

Convert 100°C to Fahrenheit:

1. 100 × 1.8 = 180
2. 180 + 32 = 212°F

The reverse: Fahrenheit to Celsius

To convert Fahrenheit back to Celsius:

°C = (°F − 32) × 5/9

Example: Convert 98.6°F (normal body temperature) to Celsius:

1. 98.6 − 32 = 66.6
2. 66.6 × 5/9 = 37°C

Quick mental conversion trick

For a rough estimate without a calculator:

• Double the Celsius value and add 30 → gives a close Fahrenheit approximation
• Example: 20°C → (20 × 2) + 30 = 70°F (actual: 68°F — close enough for weather)

Celsius to Fahrenheit conversion chart

• −40°C = −40°F (the point where both scales meet)
• 0°C = 32°F (water freezes)
• 10°C = 50°F (cool day)
• 20°C = 68°F (room temperature)
• 25°C = 77°F (warm day)
• 37°C = 98.6°F (normal body temperature)
• 40°C = 104°F (high fever / very hot day)
• 100°C = 212°F (water boils at sea level)

When is Celsius used vs Fahrenheit?

Celsius is the standard in most of the world — used in science, medicine, cooking, and everyday weather in Europe, Asia, Africa, South America, and Australia.

Fahrenheit is primarily used in the United States, along with a few other countries. If you see a weather forecast saying 95°F, that is 35°C — a very hot day.

In scientific and medical contexts, Celsius and Kelvin are preferred. Kelvin is Celsius shifted by 273.15 (0K = −273.15°C, absolute zero).

Common temperature reference points

• Freezing point of water: 0°C / 32°F
• Room temperature: ~20–22°C / 68–72°F
• Body temperature: 37°C / 98.6°F
• Boiling point of water: 100°C / 212°F (at sea level)
• Oven (moderate heat): 175°C / 350°F
• Oven (high heat): 230°C / 450°F

Convert temperatures instantly

Use the free Celsius to Fahrenheit converter on ConvertWiki to convert any temperature instantly. You can also convert Fahrenheit to Celsius and explore other unit conversion tools for length, weight, speed, and more.

Summary

The Celsius to Fahrenheit formula is (°C × 1.8) + 32. Key reference points: 0°C = 32°F (freezing), 100°C = 212°F (boiling), 37°C = 98.6°F (body temperature). For quick daily conversions, use the online temperature converter.