How to Convert Fahrenheit to Celsius
Converting Fahrenheit to Celsius is a simple three-step process. Whether you need to convert oven temperatures for a recipe, understand weather forecasts from another country, or interpret medical readings, this guide teaches you the exact formula and quick mental math shortcuts to convert °F to °C accurately every time.
The Conversion Formula
32°F = 0°C (freezing point)
212°F = 100°C (boiling point)
Alternate form: °C = (°F - 32) / 1.8
Step-by-Step Guide
Try converting values:
Open Converter →Three Easy Steps
Step 1: Subtract 32
The first step is to subtract 32 from your Fahrenheit temperature. This accounts for the offset between the two scales (water freezes at 32°F but 0°C).
Example: 72°F → 72 - 32 = 40
Step 2: Multiply by 5
Take the result from Step 1 and multiply it by 5. This is the first part of applying the ratio between the two scales.
Example: 40 × 5 = 200
Step 3: Divide by 9
Finally, divide by 9 to complete the conversion. The factor 5/9 reflects that a Celsius degree is 1.8 times larger than a Fahrenheit degree.
Example: 200 ÷ 9 = 22.22°C
Worked Examples
Example 1: 72°F (Room Temperature)
Step 1: 72 - 32 = 40
Step 2: 40 × 5 = 200
Step 3: 200 ÷ 9 = 22.22°C
72°F is the standard room temperature in the US, equivalent to a comfortable 22.22°C.
Example 2: 98.6°F (Body Temperature)
Step 1: 98.6 - 32 = 66.6
Step 2: 66.6 × 5 = 333
Step 3: 333 ÷ 9 = 37°C
98.6°F is the average normal human body temperature, which converts to a clean 37°C.
Example 3: 350°F (Oven Temperature)
Step 1: 350 - 32 = 318
Step 2: 318 × 5 = 1590
Step 3: 1590 ÷ 9 = 176.67°C
350°F is the most common baking temperature, equal to about 177°C (often rounded to 180°C in metric recipes).
Quick Shortcut: Mental Math
The Easy Estimate Method
Subtract 30, then divide by 2 for a fast approximation.
Example with 72°F:
1. Subtract 30: 72 - 30 = 42
2. Divide by 2: 42 ÷ 2 = 21°C
3. Actual answer: 22.22°C
This shortcut is within a few degrees of the exact answer and works well for everyday temperatures. The approximation is most accurate around 50-80°F.
Practice the Shortcut
Try these yourself:
50°F:
(50 - 30) / 2 = 10°C
Exact: 10°C (perfect match!)
86°F:
(86 - 30) / 2 = 28°C
Exact: 30°C (close!)
32°F:
(32 - 30) / 2 = 1°C
Exact: 0°C (close enough!)
Common Mistakes to Avoid
Forgetting to Subtract 32 First
The most common mistake is multiplying by 5/9 before subtracting 32. You must subtract 32 first because the Fahrenheit and Celsius scales have different zero points. If you skip this step, your answer will be significantly wrong. Always follow the order: subtract 32, then multiply by 5/9.
Confusing the Formula Direction
People often mix up which formula to use. Remember:
°F to °C: °C = (°F - 32) × 5/9
°C to °F: °F = °C × 9/5 + 32
A helpful way to remember: when going to Celsius (the smaller scale), you subtract and use the smaller fraction (5/9). When going to Fahrenheit (the larger scale), you multiply and add.
Quick Reference Table
| °F | °C | Description |
|---|---|---|
| 0 | -17.78 | Very cold |
| 32 | 0 | Freezing point |
| 50 | 10 | Cool |
| 68 | 20 | Comfortable |
| 72 | 22.22 | Room temp |
| 77 | 25 | Warm |
| °F | °C | Description |
|---|---|---|
| 86 | 30 | Hot day |
| 98.6 | 37 | Body temp |
| 100 | 37.78 | Very hot |
| 212 | 100 | Boiling point |
| 350 | 176.67 | Baking |
| 400 | 204.44 | High baking |