Fahrenheit to Celsius Converter
Convert degrees Fahrenheit to degrees Celsius in one step. Negative temperatures and decimals are fully supported, with the formula and common values shown below.
Celsius = (Fahrenheit − 32) × 5/9
Fahrenheit to Celsius Formula
To convert Fahrenheit to Celsius, subtract 32 from the Fahrenheit temperature and then multiply the result by 5/9 (about 0.5556). The subtraction aligns the two zero points, and the 5/9 factor adjusts for the different size of each degree. The same formula works for negative values and decimals. To convert back, multiply by 9/5 and add 32.
Fahrenheit and Celsius Explained
Fahrenheit (°F) was proposed by the physicist Daniel Gabriel Fahrenheit in the early 1700s. On this scale water freezes at 32 °F and boils at 212 °F at standard sea-level pressure, so there are 180 degrees between the two points. It is used for everyday weather, cooking and body temperature mainly in the United States and a few other places.
Celsius (°C) divides the same range into 100 degrees, with water freezing at 0 °C and boiling at 100 °C. It is used for weather, cooking and science in most of the world, and it is tied directly to the kelvin scale: 0 °C is 273.15 K.
Because the two scales have different zero points as well as different degree sizes, you cannot simply multiply. You must subtract 32 first.
How to Convert Fahrenheit to Celsius
- Enter the temperature in °F. Decimals such as 98.6 work, and you can type a minus sign for negative values or use the Toggle sign button on a phone.
- The Celsius result appears instantly, or press Convert Now.
- Use Swap Units to convert Celsius to Fahrenheit, Copy Result to copy the answer, or Clear to start again.
Step-by-step by hand
- Write down the temperature in °F, for example 77 °F.
- Subtract 32: 77 − 32 = 45.
- Multiply by 5/9: 45 × 5 ÷ 9 = 25.
- Add the unit: 77 °F = 25 °C.
Working with negative Fahrenheit values
Do not skip or reverse the subtraction. For −4 °F: −4 − 32 = −36, then −36 × 5/9 = −20 °C. For 14 °F: 14 − 32 = −18, then −18 × 5/9 = −10 °C. A positive Fahrenheit reading can still be a negative Celsius one, because anything below 32 °F is below freezing.
For a quick mental estimate, subtract 30 and halve the result. 70 °F gives (70 − 30) ÷ 2 = 20 °C, against the exact 21.11 °C. The converter rejects values below absolute zero (−459.67 °F), since no temperature can be lower.
Practical Examples
- Body temperature: (98.6 − 32) × 5/9 = 37 °C. A fever reading of 101.5 °F is 38.61 °C.
- Room temperature: 72 °F = 22.22 °C.
- Oven setting: 350 °F = 176.67 °C, and 425 °F = 218.33 °C.
- Hot summer day: 100 °F = 37.78 °C.
- Freezing winter day (negative result): 0 °F = -17.78 °C, and 20 °F = -6.67 °C.
- Negative Fahrenheit input: −10 °F = -23.33 °C, and −40 °F = -40 °C.
Values here are rounded to two decimals for readability. The converter keeps full precision internally.
Fahrenheit to Celsius – Common Values
Quick reference for frequently used conversions
| Fahrenheit (°F) | Celsius (°C) | Kelvin (K) |
|---|---|---|
| -40 °F | -40 °C | 233.15 K |
| -30 °F | -34.44 °C | 238.71 K |
| -20 °F | -28.89 °C | 244.26 K |
| -10 °F | -23.33 °C | 249.82 K |
| 0 °F | -17.78 °C | 255.37 K |
| 10 °F | -12.22 °C | 260.93 K |
| 20 °F | -6.67 °C | 266.48 K |
| 32 °F | 0 °C | 273.15 K |
| 40 °F | 4.44 °C | 277.59 K |
| 50 °F | 10 °C | 283.15 K |
| 60 °F | 15.56 °C | 288.71 K |
| 68 °F | 20 °C | 293.15 K |
| 70 °F | 21.11 °C | 294.26 K |
| 72 °F | 22.22 °C | 295.37 K |
| 80 °F | 26.67 °C | 299.82 K |
| 90 °F | 32.22 °C | 305.37 K |
| 98.6 °F | 37 °C | 310.15 K |
| 100 °F | 37.78 °C | 310.93 K |
| 104 °F | 40 °C | 313.15 K |
| 150 °F | 65.56 °C | 338.71 K |
| 212 °F | 100 °C | 373.15 K |
| 250 °F | 121.11 °C | 394.26 K |
| 300 °F | 148.89 °C | 422.04 K |
| 350 °F | 176.67 °C | 449.82 K |
| 400 °F | 204.44 °C | 477.59 K |
| 450 °F | 232.22 °C | 505.37 K |
Where and Why This Conversion Is Used
The United States and a handful of other countries use Fahrenheit, while the rest of the world uses Celsius, so travellers, cooks and students convert between the two all the time.
- Weather and travel: a forecast of 85 °F sounds mild until you convert it to 29.44 °C and realise it is a hot day.
- Cooking and baking: American recipes give oven temperatures in °F, while many ovens abroad are marked in °C.
- Health: thermometers and medical advice differ by region, and a fever threshold of 100.4 °F is 38 °C.
- Science and engineering: lab work is usually in °C or K, while US equipment manuals and datasheets often list °F.
- Home and appliances: thermostats, water heaters, freezers and pool thermometers are labelled in different units depending on the market.
To convert the other way, use the Celsius to Fahrenheit Converter.