Enter a Fahrenheit temperature to find its Celsius equivalent, or switch directions to convert a Celsius reading to Fahrenheit.
Advanced options
Results use 1 decimal place and Automatic number format unless you change these options.
This converts a temperature reading, not a temperature change. A temperature change does not use the 32-degree offset.
Table of contents
How to use our Fahrenheit to Celsius Converter
- Choose the conversion direction that matches the scale printed beside your source temperature.
- Enter one temperature in the visible field. Negative numbers and decimals are valid.
- Click Calculate to see the converted temperature and the calculation step used.
- Open Advanced options if you need a specific number of decimal places or scientific notation.
- Check a familiar value when possible: 32 degrees F is 0 degrees C, 212 degrees F is 100 degrees C, and -40 is the same on both scales.
Definitions
Fahrenheit (degrees F): A temperature scale commonly used in the United States.
Celsius (degrees C): A temperature scale used in science and in most countries.
Temperature reading: The temperature at one moment, such as 68 degrees F. Converting a reading uses a scale factor and a 32-degree offset.
Temperature change: The difference between two readings, such as a rise of 18 degrees F. Converting a change does not use the 32-degree offset.
Scientific notation: A compact way to write a very large or very small number, such as 1.2 x 106.
Common mistakes and quick fixes
Mistake: Entering a Fahrenheit number while Celsius to Fahrenheit is selected.
Fix: Check Conversion direction and then recalculate. Choose the direction based on the scale of the number you have, not the scale you want to get.
Mistake: Expecting 32 degrees F to equal 32 degrees C.
Fix: Check Conversion direction and then recalculate. The scales have different zero points. Entering 32 degrees F gives 0 degrees C.
Mistake: Typing a range such as "20-30" or two values such as "20 30".
Fix: Check Conversion direction and then recalculate. Enter one finite temperature at a time, then calculate each reading separately.
Mistake: Using the reading formula for a temperature rise or drop.
Fix: Check Conversion direction and then recalculate. This converter is for temperature readings. For a Fahrenheit temperature change, multiply by 5/9 without subtracting 32.
Mistake: Treating a rounded display as an exact measurement.
Fix: Increase Result decimal places if your thermometer, report, or assignment requires more shown detail.
Limitations & Key Assumptions / Boundary Conditions
- This calculator converts temperature readings between Fahrenheit and Celsius. Do not use the 32-degree offset formula for a temperature increase or decrease.
- The converted value cannot be more accurate than the original weather report, thermostat, recipe, or thermometer reading.
- Decimal-place settings change only the displayed rounding, not the underlying calculation.
- Automatic number format uses scientific notation only for extremely large or small finite results.
- Each calculation needs one finite number. Blank entries, ranges, formulas, multiple numbers, NaN, and Infinity are rejected.
Methodology
Conversion method
Temperature readings use a fixed 32-degree offset between the Fahrenheit and Celsius scales, plus an exact scale factor. [1]
degrees C = (degrees F - 32) × 5/9
degrees F = (degrees C × 9/5) + 32
Worked example
To convert 98.6 degrees F, subtract 32 first: 98.6 - 32 = 66.6. Then multiply by 5/9, giving 37 degrees C.
(98.6 - 32) × 5/9 = 37
The calculator keeps the converted value unrounded until it formats the displayed answer using your selected decimal places and number format.