# Formula to Convert Fahrenheit to Celsius

**Celsius**, as well as **Fahrenheit**, are both the **temperature scales**. Celsius is the temperature scale for the **metric system** and Fahrenheit for the **imperial system**.

Scale | Melting point | Boiling point |

C | 0 | 100 |

F | 32 | 212 |

The points on the above table refer to pure water points at atmospheric pressure at sea level.

From the above numbers, one may easily deduct the equation to convert degrees Fahrenheit into degrees Celsius:

C / 5 = ( F – 32 ) / 9

An easy way to convert F to C with acceptable precision, without a calculator in hands, is:

1. Take F temperature and subtract 32.

2. Divide the result by 2.

3. Add 10% to the result.

**Example** to convert 72 F to C:

72 – 32 = 40

40 / 2 = 20

20 + 10% = 22

**Result: **72 F = 22 C (from the equation it should be 22.22)

In **INDIA** we calculate in **Celsius**. 1 degree Celsius is 33.8 degrees Fahrenheit. The United States relies heavily on **Fahrenheit**. While Americans sometimes use Celsius particularly in the medical and scientific fields. Nearly all countries switched over to Celsius in the 1970′s as a move to standardize on the metric measurement system. Other than the U.S, countries that use the Fahrenheit temperature scale are the Bahamas, Belize, the Cayman Islands, Palau, and sometimes Canada and the U.K. (both predominantly use Celsius).

One degree Celsius is 9/5 times large than a degree Fahrenheit.

On the Celsius, scale water boils at 100C and melts at 0C whereas it is 212 and 32F respectively. Most of the world uses Celsius because it is sensible and also because the C matches the size of the Kelvin, the unit of temperature in the SI system of units. Even the staid old UK uses Celsius now.

The USA and some small territories associated stay welded to the old fashioned units.

1 °C is one degree above the 0 °C

1 °F = -17.22 °C

-17 °C is under the 0 °C Scale

THE DIFFERENCE is 18.22 ° on the Celsius scale, i.e.1 °C = 33.8 °F on the Fahrenheit scale the difference is 32.8 °F

32.8/18.22 °C = 1.8 degree

The difference: 1°C – 1°F = 1°C – (-17.2°C) = 18.2°C = 64.8°F

**Formula is-**

(9/5)*C = F to convert Celsius degrees into Fahrenheit degrees. Therefore

-40°C = 40°F

-17.8°C = 0°F

-17.2°C = 1°F

0°C = 32.0°F

1°C = 33.8°F

100°C = 212°F

**Conversion of Celsius to Fahrenheit scale and vice versa:**

Five degrees of Celsius temperature equals 9 degrees Fahrenheit temperature. The frigid temperature of the water is ‘0’ degrees Celsius and 32 degrees Fahrenheit. We need to adjust twice, once for the difference in the ‘0’ marks and second for the difference in the size of a degree.

First, subtract 32 from the Fahrenheit temperature so that we get how many degrees you are away from the freezing point of water. So if the Fahrenheit temperature was 50, you have 18 so far. If the Fahrenheit temperature was -20, now you have -52.

Secondly, multiply the number you got by five and divide by 9.

From Centigrade to Fahrenheit:

Multiply by nine on five

Add 32 to the result.

To get the number for which you did strive.

**Fahrenheit into Centigrade**

Subtract 32 and multiply the answer by nine below five.

To brief it, the conversion from C to F requires to multiply the temperature in C by 1.8 (each change of 1 degree C represents a change of 1.8 degrees F) and add the offset of 32 (32 degrees F = 0 degrees C).

A quick way to do it without calculation is to “double it and add 30”. So 20 degrees C would be about 2*20 + 30 = 40+30 = 70 degrees F. The actual answer is 68, but 70 is close. The conversion is exactly right at 10 degrees C (50 degrees F) but diverges from there, so the further you are from 10 degrees C, the less accurate this estimation is.

To understand how the formula came about, they are two different scales, and there is a straight relationship between the two scales. It means, a graph plot with the temperature in C and F, will fall in a straight line. The formula is nothing but the equation for the straight line.

Water boils at 100 C in the Celsius scale, and when observed in the Fahrenheit scale it is 212 F. Similarly if observed the freezing point, it is 0 C and 32 F. So we have a c1, f1, and c2, f2.

Equation of the line connecting C and F would be F = mC + b

Equation 1: 32 = 0*m + b; thus b = 32

Equation 2: 212 = 100m + 32; Thus m = (212-32)/100 = 9/5

Hence the formula; F = (9/5)*C + 32

**Example** of converting Fahrenheit temperature to Celsius temperature use the formula.

C= (F-32) x 5/9

For example- to convert -40°F to Celsius temperature, then C=( -40–32) x 5/9= -72 x 5/9= -40

F=(C x 9/5) + 32. For example in order to convert 100°C to Fahrenheit, F= (100 x 9/5) + 32= 180+32=212°F