How to Convert Celsius to Fahrenheit: Formula, Key Temperatures & Quick Guide
Learn how to convert Celsius to Fahrenheit with the exact formula, key temperature references, and practical tips for weather, cooking, and travel.
February 19, 2026
Temperature conversion between Celsius and Fahrenheit is one of the most common conversions people encounter in daily life. Whether you are checking weather forecasts from another country, cooking with international recipes, or traveling abroad, understanding how to switch between these two scales is essential.
The Celsius to Fahrenheit Formula
The conversion formula is simple but involves two steps: multiplication and addition. To convert Celsius to Fahrenheit, multiply the Celsius temperature by 9/5 (or 1.8) and then add 32.
Formula: °F = (°C x 9/5) + 32
For example, to convert 25°C to Fahrenheit: (25 x 1.8) + 32 = 45 + 32 = 77°F.
Key Temperature Reference Points
Memorizing a few key temperatures makes everyday conversions much easier:
- 0°C = 32°F — Water freezes
- 10°C = 50°F — Cool weather, light jacket needed
- 20°C = 68°F — Comfortable room temperature
- 25°C = 77°F — Warm and pleasant day
- 30°C = 86°F — Hot summer day
- 37°C = 98.6°F — Normal human body temperature
- 40°C = 104°F — Extreme heat or high fever
- 100°C = 212°F — Water boils
When You Need This Conversion
Weather and Travel
Most countries in the world use Celsius for weather reporting, while the United States uses Fahrenheit. When an international forecast says it will be 35°C tomorrow, that translates to 95°F, meaning you should expect very hot conditions. Conversely, a crisp 5°C day is 41°F, which calls for a warm coat.
Cooking and Baking
Oven temperatures in recipes vary by region. European and international recipes typically use Celsius, while American recipes use Fahrenheit. Common conversions include: 180°C = 356°F (standard baking), 200°C = 392°F (roasting), and 220°C = 428°F (high-heat cooking). Getting these right is critical for successful results in the kitchen.
Health and Medicine
Body temperature is a key health indicator. Normal body temperature is 37°C or 98.6°F. A fever is generally considered to begin at 38°C (100.4°F). In medical contexts, precise temperature conversion can be important for proper diagnosis and treatment, especially when using thermometers calibrated in different scales.
Reverse Conversion: Fahrenheit to Celsius
To convert Fahrenheit back to Celsius, subtract 32 and then multiply by 5/9. For example: (98.6 - 32) x 5/9 = 66.6 x 0.5556 = 37°C.
Quick Mental Math Tricks
For a rough estimate, you can use a simplified method: subtract 30 from the Fahrenheit value and divide by 2. For example, 80°F: (80 - 30) / 2 = 25°C (actual: 26.7°C). This is not exact but gives a useful ballpark figure. Another trick: remember that -40 is the same in both scales. At -40°C, the Fahrenheit reading is also -40°F, which is the only point where both scales intersect.
Why Two Temperature Scales Exist
The Fahrenheit scale was developed by Daniel Gabriel Fahrenheit in 1724, while the Celsius scale was proposed by Anders Celsius in 1742. The Celsius scale is based on the freezing and boiling points of water, making it intuitive for scientific use. Today, Celsius is the global standard, while Fahrenheit remains in daily use primarily in the United States and a few Caribbean nations.