Decimal Fahrenheit to Celsius

Direct answer

Subtract 32 from the complete decimal Fahrenheit value and multiply the result by 5/9.

For example:

Use the Fahrenheit to Celsius Converter for another decimal reading.

How to convert decimal Fahrenheit values

1. Read the complete Fahrenheit value. Preserve all decimal digits supplied by the thermometer or specification.
2. Subtract 32 from the complete value.
3. Multiply the result by 5.
4. Divide by 9.
5. Round the final Celsius result only when necessary.
6. Label the answer with °C.

Example: convert 98.6°F

Example: convert 70.7°F

Example: convert 39.2°F

Common decimal Fahrenheit conversions

Decimal values that convert to whole Celsius degrees

Many Fahrenheit temperatures with one decimal place correspond exactly to whole Celsius values.

Why the decimal portion must be preserved

Rounding a Fahrenheit reading before conversion can change the result.

Compare 72.5°F and 73°F

The difference may be unimportant in casual conversation but can matter for thermometer readings, appliances, scientific work, or temperature thresholds.

Converting negative decimal temperatures

Keep the negative sign and decimal portion throughout the calculation.

Example: convert -0.4°F

Example: convert -22.9°F

How many decimal places should be kept?

The proper rounding level depends on the source measurement and application.

• Whole degrees may be enough for a general weather forecast.
• One decimal place may suit many thermometers and thermostats.
• Two decimal places can support detailed comparisons.
• Laboratory or technical work may require more precision.

A device showing Fahrenheit to one decimal place does not normally support claiming that the Celsius temperature was physically measured to ten decimal places.

Example of rounding a repeating result

Convert 71.3°F:

Where decimal Fahrenheit readings are common

• digital body thermometers;
• weather stations;
• thermostats;
• refrigerator and freezer sensors;
• aquarium and pool thermometers;
• industrial temperature probes;
• scientific instruments;
• oven and cooking thermometers.

Decimal input and displayed precision

A calculator may display more decimal places than the source instrument. This can be useful for mathematical accuracy, but the final reported result should reflect the quality of the original measurement.

Common decimal conversion mistakes

Dropping the decimal portion

Convert 98.6°F as 98.6, not 98°F or 99°F.

Rounding the input before conversion

Keep the original reading and round the final Celsius value.

Applying the formula only to the decimal digits

The entire Fahrenheit value must be placed inside the parentheses.

Using the mental shortcut for precise readings

Subtracting 30 and dividing by 2 is only an approximation.

Displaying unsupported precision

Match the final number of decimal places to the original thermometer or specification.

Related Fahrenheit to Celsius guides

Frequently asked questions