How do I convert Fahrenheit to Celsius?
Use the formula deg C = (deg F - 32) * 5/9. Enter any deg F value and CalcuNimble calculates deg C instantly.
Convert Fahrenheit to Celsius
Use this deg F to deg C converter for fast everyday calculations, quick reference values, and the exact formula behind the result.
Fahrenheit to Celsius Converter
Convert Fahrenheit (deg F) to Celsius (deg C) instantly.
Fahrenheit to Celsius: master the reverse conversion for weather, health, and home
If you grew up with Fahrenheit but now live or travel where Celsius is the norm, reversing the conversion quickly becomes a practical skill. From interpreting a weather report to adjusting a thermostat, this guide walks you through the formula and common rounding strategies.
Formula
The reverse formula is deg C = (deg F - 32) * 5/9. Subtract 32 from the Fahrenheit reading first, then multiply the result by 5 and divide by 9. The subtraction removes the offset between the two scales before scaling to Celsius degrees.
Worked example
A weather forecast says 77 °F. Subtract 32 to get 45, then multiply by 5/9: 45 × 5 = 225, divided by 9 equals exactly 25 °C. This is a comfortable room temperature in most parts of the world — warm enough for short sleeves without being uncomfortably hot.
Common Reference Values
| Fahrenheit | Celsius | Context |
|---|---|---|
| -40.00 deg F | -40.000 deg C | Extreme cold |
| 32 deg F | 0.000 deg C | Freezing point (F) |
| 68 deg F | 20 deg C | Room temperature (F) |
| 98.6 deg F | 37 deg C | Body temperature (F) |
| 212 deg F | 100 deg C | Boiling point (F) |
Practical guidance
Body temperature and health monitoring
Medical guidelines often quote fever thresholds in Celsius (38 °C and above), but thermometers in many households read Fahrenheit. Knowing that 100.4 °F equals 38 °C lets you interpret readings without second-guessing. Always wait a few minutes after eating or drinking before taking an oral temperature — the conversion is only as reliable as the measurement itself.
Rounding: when whole degrees are enough
For weather, rounding to the nearest whole degree Celsius is usually sufficient — nobody dresses differently for 21 °C versus 21.7 °C. For scientific work, cooking, or medical readings, keep one decimal place. The formula itself introduces no rounding error, so any loss of precision comes from how you handle the final number.
Subtracting before multiplying — order matters
A frequent error is applying 5/9 first and then subtracting 32, which yields a wildly incorrect result. The subtraction must happen first because it removes the offset. If you reverse the order, you get a number that is off by roughly 17.8 degrees. When in doubt, use the converter above — it handles the order for you.
Frequently asked questions
What is the deg F to deg C formula?
deg C = (deg F - 32) * 5/9
Can I use decimals for deg F to deg C?
Yes. The converter supports decimal input and shows up to 6 decimal places for accurate daily use.
When is deg F to deg C conversion commonly used?
Useful for weather checks, baking, and travel between Celsius and Fahrenheit regions.
How can I convert Celsius back to Fahrenheit?
Use the swap button in the converter card or open deg C to deg F at /convert/c-to-f/.