Fahrenheit to Celsius Converter

1. Enter the temperature in degrees Fahrenheit. The Celsius answer appears straight away.
2. Choose the decimal places. Fahrenheit readings rarely land on a whole Celsius number, so one or two decimals help.
3. Read the Celsius result and the band below it. Use the bulk box for a week of forecast highs or a list of recipe settings.

On this page, deg F stands for degrees Fahrenheit and deg C for degrees Celsius. The tool prints the real degree sign.

A Fahrenheit to Celsius conversion takes a temperature written in degrees Fahrenheit and expresses it in degrees Celsius, the unit most of the world uses for weather, cooking and science classes.

The Fahrenheit scale puts the freezing point of water at 32 and the boiling point at 212, which is 180 degrees apart. Celsius puts the same two points at 0 and about 100. A conversion therefore has to remove the 32 offset first and then shrink the degrees by the ratio 100/180, which is 5/9.

This is the direction people need when the source is American. Examples include a US weather report, a recipe from a US website, a thermostat set in Fahrenheit, or the temperature limits printed on a US appliance. Readers outside the United States usually think in Celsius and want the number in their own terms.

The conversion changes the label, not the heat. A room at 72 deg F and a room at 22.22 deg C are equally warm.

The formula first lines up the freezing points by subtracting 32, then rescales the result by dividing by 1.8.

1. Subtract 32 from the Fahrenheit value. Example: 72 - 32 = 40.
2. Divide by 1.8, or multiply by 5/9. Example: 40 / 1.8 = 22.22 deg C.
3. Check by reversing: 22.22 x 1.8 + 32 = 72 deg F, within rounding.

NIST SP 811 lists this relation as t/deg C = (t/deg F - 32)/1.8. Subtract before you divide. Doing it the other way round is the classic error in this direction.

Because 5/9 is 0.5555 repeating, most Fahrenheit readings give a Celsius answer with endless decimals. The exceptions are steps of 9 deg F from 32: the values 32, 41, 50, 59, 68, 77 and 86 give exactly 0, 5, 10, 15, 20, 25 and 30 deg C.

A US forecast high of 95 deg F. 95 - 32 = 63, and 63 / 1.8 = 35 deg C. That is a very hot day by any standard.

A thermostat at 72 deg F. 72 - 32 = 40, and 40 / 1.8 = 22.22 deg C. A setting of 68 deg F is exactly 20 deg C.

A cookie recipe at 350 deg F. 350 - 32 = 318, and 318 / 1.8 = 176.67 deg C. Metric ovens are set to 180 for this. NIST lists 350 deg F and 180 deg C as approximate equals for a moderate oven.

A fridge at 40 deg F and a freezer at 0 deg F. The US Food and Drug Administration says to keep a refrigerator at 40 deg F or below and a freezer at 0 deg F. Those limits are 4.44 deg C and -17.78 deg C.

A winter low of 14 deg F. 14 - 32 = -18, and -18 / 1.8 = -10 deg C. The subtraction gives a negative number, and the minus sign carries through.

Cooking meat is a case where the exact figure matters more than a rounded dial. Our guide to meat cooking times and temperatures lists the usual targets.

The math is fixed. These four points decide whether the answer is useful.

Reading or Difference

A reading of 50 deg F is 10 deg C. A difference of 50 deg F, such as the gap between a 30 deg F night and an 80 deg F day, is 27.78 Celsius degrees. Differences skip the "subtract 32" step and use only the 5/9 factor.

Repeating Decimals

Since most answers never end, the decimal setting matters more here than in the other direction. 100 deg F is 37.777... deg C. It shows as 38 with no decimals, 37.8 with one and 37.78 with two.

Rounded Settings on Metric Devices

Metric ovens and thermostats move in round Celsius steps. The exact 204.44 deg C for 400 deg F is set as 200. The exact value is still the right one for a probe thermometer.

Values Below Zero

Fahrenheit and Celsius both run below zero, but at different places. 0 deg F is already -17.78 deg C. Every Fahrenheit reading under 32 gives a negative Celsius result.

The usual mental rule is "take away 30, then halve". It is exact at 50 deg F and drifts as you move away. The error is (5 - 0.1 x deg F) / 1.8, in Celsius degrees.

For outdoor temperatures between 32 and 68 deg F the estimate is within 1 deg C, which is fine for choosing a coat. It is not good enough for an oven, a fridge check or a thermometer reading.

A Closer Mental Method

Subtract 32, halve the result, then add one tenth of that half, and then one hundredth of it. For 100 deg F: 68, then 34, plus 3.4, plus 0.34 gives 37.74. The true value is 37.78. This method multiplies by 0.555 in place of 0.5556, so it runs about 0.1 percent low.

Following US Weather from Abroad

US forecasts, storm warnings and heat advisories quote Fahrenheit. Converting the high and the low tells a visitor what to pack. Humid air changes how heat feels, so a muggy day also calls for the dew point calculator.

Cooking American Recipes in a Metric Kitchen

US recipes give oven heat in Fahrenheit, often in 25-degree steps from 300 to 450. Convert, then pick the nearest setting your oven offers. The oven temperature guide covers gas marks as well.

Checking Appliance and Storage Limits

Manuals for US appliances state limits in Fahrenheit. The refrigerator and freezer limits from the FDA, 40 deg F and 0 deg F, are 4.44 deg C and -17.78 deg C.

Reading a Fahrenheit Thermometer

A US thermometer that shows 98.6 deg F is showing 37 deg C. For that single task, the body temperature converter is quicker. It converts the number only and cannot assess health.

Exact values from deg C = (deg F - 32) / 1.8, shown to 2 decimals.

Values That Convert to Whole Numbers

Common US Readings

US Oven Settings

The metric setting column rounds to common oven steps and agrees with the approximate oven table published by NIST.

1. Dividing Before Subtracting

68 / 1.8 - 32 gives 5.78. The right answer is 20. Take away 32 first.

2. Multiplying by 9/5

(68 - 32) x 1.8 gives 64.8. The fraction 9/5 belongs to the Celsius to Fahrenheit direction.

3. Subtracting 32 from a Difference

A 10 deg F drop overnight is a 5.56 deg C drop. Running it through the full formula gives -12.22, which is a reading, not a change.

4. Rounding 5/9 to 0.5

Halving turns 350 deg F into 159 deg C. The exact figure is 176.67, so the oven would run almost 18 degrees too cool.

5. Expecting a Whole Number

72 deg F is 22.22 deg C, not 22. Reporting it as 22 and converting back gives 71.6 deg F.

6. Mixing Up 0 Deg F and 0 Deg C

0 deg F is far colder than freezing. It equals -17.78 deg C.

The result is exact to the decimals shown. The constants 32 and 1.8 are defined values, so the only rounding is in the display.

100 deg F is 37.78 deg C. Subtract 32 to get 68, then divide by 1.8.

350 deg F is 176.67 deg C. Metric recipes and ovens round this to 180 deg C.

0 deg F is -17.78 deg C. It is the freezer temperature the US FDA recommends, and it is well below the freezing point of water.

72 deg F is 22.22 deg C. A thermostat set to 22 deg C is the closest whole-number match.

Fahrenheit places the freezing point of water at 32, while Celsius places it at 0. Removing 32 makes both scales start from the same point before the degrees are resized.

Yes. 5/9 is the inverse of 9/5, and 9/5 is 1.8. Multiplying by 5/9 and dividing by 1.8 give the same result.

Neither. -40 is the one point where the two scales agree, so both describe the same temperature.

Daniel Fahrenheit unveiled it in 1724, according to NIST. The scale was later fixed so that water freezes at 32 degrees and boils at 212 degrees.

Type =(A2-32)/1.8 in a cell, with the Fahrenheit value in A2. Keep the brackets, or the sheet will divide 32 by 1.8 first.

A change of 1 deg F equals a change of 5/9 deg C, about 0.556. A change of 9 deg F is exactly 5 deg C.

No. Everything runs in your browser. A saved result stays in your own browser storage until you clear it.

• Conversion relations from degree Fahrenheit to degree Celsius and to kelvin (NIST SP 811, Appendix B.8).
• Exact temperature conversion table and approximate oven temperature equivalences (NIST Office of Weights and Measures).
• How Daniel Fahrenheit set up his scale in 1724 (NIST, Kelvin: History).
• Refrigerator at 40 deg F or below and freezer at 0 deg F (US Food and Drug Administration).