How To Convert F To C

This post will teach you how to convert from Fahrenheit to Celsius. We have done the research and the math for you, all you have to do is follow and understand the instructions below.

Fahrenheit and Celsius are the scales most often used for reporting room, weather, and water temperatures. The Fahrenheit scale is used in the United States, while the Celsius scale is used worldwide. Indeed, most countries around the world measure their weather and temperatures using the relatively simple Celsius scale. But the United States is one of just a few remaining countries that use Fahrenheit, so it’s important for Americans to know how to convert one to the other, especially when traveling or doing scientific research.

Table of Contents

Celsius Scale

Celsius, or centigrade, is a scale and unit of measurement for temperature. It is one of the most commonly used temperature units. Celsius, also known as centigrade, is a scale to measure temperature. The unit of measurement is the degree Celsius (°C). It is one of the most commonly used temperature units in the world. The unit system is named after the Swedish astronomer Anders Celsius (1701-1744), who developed a similar temperature scale.

From 1743 until 1954, 0°C was defined as the freezing point of water, and 100°C was defined as the boiling point of water, both at a pressure of one standard atmosphere, with mercury as the working material. Although these defining correlations are commonly taught in schools today, by international agreement the unit “degree Celsius” and the Celsius scale are currently defined by two different temperatures: absolute zero and the triple point of Vienna Standard Mean Ocean Water (VSMOW; specially purified water).

Besides expressing specific temperatures along its scale (e.g., “Gallium melts at 29.7646°C” and “The temperature outside is 23 degrees Celsius”), the degree Celsius is also suitable for expressing temperature intervals — differences between temperatures, or their uncertainties (e.g. “The output of the heat exchanger is hotter by 40 degrees Celsius” and “Our standard uncertainty is ±3°C”). Because of this dual usage, one must not rely upon the unit name or its symbol to denote that a quantity is a temperature interval; it must be clear through context or explicit statement that the quantity is an interval.

Fahrenheit Scale

How did the Fahrenheit temperature scale come into existence? The first mercury thermometer was invented by German scientist Daniel Fahrenheit in 1714. His scale divides the freezing and boiling points of water into 180 degrees, with 32 degrees as water’s freezing point, and 212 as its boiling point.

On Fahrenheit’s scale, zero degrees was determined as the temperature of a temperature-stable brine solution of ice, water, and ammonium chloride. He based the scale on the average temperature of the human body, which he originally calculated at 100 degrees. (As noted, it’s since been adjusted to 98.6 degrees Fahrenheit.)

Fahrenheit was the standard unit of measure in most countries until the 1960s and 1970s when it was replaced with the Celsius scale in a widespread conversion to the more useful metric system. In addition to the United States and its territories, Fahrenheit is still used in the Bahamas, Belize, and the Cayman Islands for most temperature measurements.

The Conversion Process

Use this formula to get a good estimate of the Celsius temperature when converting from Fahrenheit. In this case means divided by or to use division.

(Fahrenheit temp. [F]-30)/2 = Celsius temp.

In other words, if you’d like to convert a Fahrenheit temperature to an approximate Celsius temperature:

  1. Start with the temperature in Fahrenheit (e.g., 100 degrees).
  2. Subtract 30 from this figure (e.g., 100 – 30 = 70).
  3. Divide your answer by 2 (e.g., 70 / 2 = 35).

If you want a more precise calculation, you can use the more exact formula:

  • C = 5/9 x (F-32)

The notation C represents the temperature in Celsius, and F is the temperature in Fahrenheit. After you know the formula, it is easy to convert Fahrenheit to Celsius with these three steps.

  1. Subtract 32 from the Fahrenheit temperature.
  2. Multiply this number by five.
  3. Divide the result by nine.

For example, suppose the temperature is 80 degrees Fahrenheit and you want to know what the figure would be in Celsius. Use the above three steps:

  1. 80 F – 32 = 48
  2. 5 x 48 = 240
  3. 240 / 9 = 26.7 C

So the temperature in Celsius is 26.7 C.


If you want to convert a normal human body temperature (98.6 F) to Celsius, plug the Fahrenheit temperature into the formula:

C = 5/9 x (F – 32)

As noted, your starting temperature is 98.6 F. So you would have:

C = 5/9 x (F – 32)

C = 5/9 x (98.6 – 32)

C = 5/9 x (66.6)

C = 37 C

Check your answer to ensure it makes sense. At ordinary temperatures, a Celsius value is always lower than the corresponding Fahrenheit value. Also, it’s helpful to keep in mind that the Celsius scale is based on the freezing and boiling points of water, where 0 C is the freezing point and 100 C is the boiling point. On the Fahrenheit scale, water freezes at 32 F and boils at 212 F.

Conversion Shortcut

You often don’t need an exact conversion. If you’re traveling to Europe, for example, and you know the temperature is 74 F, you might want to know the approximate temperature in Celsius. The website Lifehacker offers this tip on making an approximate conversion:

Subtract 30 from the Fahrenheit temperature and then divide by two. So, using the approximation formula:

  • 74 F – 30 = 44
  • 44 / 2 = 22 C

(If you go through the previous formula’s calculations for the exact temperature, you arrive at 23.3.)

Quick Conversion Table

You can save even more time by using predetermined conversions. The Old Farmer’s Almanac offers this table for making quick conversions from Fahrenheit to Celsius.

-40 F-40 C
-30 F-34 C
-20 F-29 C
-10 F-23 C
0 F-18 C
10 F-12 C
20 F-7 C
32 F0 C
40 F4 C
50 F10 C
60 F16 C
70 F21 C
80 F27 C
90 F32 C
100 F38 C


The conversion of temperature is also important to many people, because the temperature is used to help you know how to dress properly, or what the conditions are on the outside.

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