Temperature Conversion Formulas

Easy Temperature Conversion Formula

Formula to convert Temperatures is relevant when we seek to change the value of temperature from one unit to another. There are a number of temperature conversion formulas and methods. Among them, Celsius, Fahrenheit, and Kelvin are the most often applied methods throughout the world. Each measuring scale has its own uses. Where Celsius and Fahrenheit are represented using degree scales. The degree symbol is not used to record temperature using the Kelvin scale, instead reported as Kelvins. Whether we incorporate Celsius, Fahrenheit, or Kelvin in our attempts to measure temperatures, is not that relevant. However, if we see ourselves in regions with different temperature measurement, then knowing the differences between the three commonly used systems may prove useful.

Temp Conversion Formulas

There can be mainly 3 common conversions of temperature which are:

  • Conversion from Celsius to Kelvin

  • Conversion from Celsius to Fahrenheit

  • Conversion from Fahrenheit to Kelvin

The figure is shown below clearly depicts various temperature conversion formulas;-

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Useful Temperature Conversion Facts

  • Water boils at a point of 100°C, 212°F or 373.15K

  • Water freezes at a point of 0°C and 32°F or 273.15K

  • Celsius and Fahrenheit measure exactly the same at -40°. It is because the scales converge.

  • Absolute zero refers to 0 K. This is the lowest temperature any matter can drop down to.

  • 0°C equals 32°F

  •  0°C equals 273.15 Kelvins

  • At high temperatures, Celsius and Kelvin become equal since the difference of 273.15 between them withdraws in the noise.

  • Temperature can be simply described as a computation of the hotness or coldness of a substance

  • Temperature is studied using a thermometer – we notice the effect of temperature on the compound inside it.

Common Temperature Conversions

A. Celsius

Also called centigrade, this scale based system was invented by the Swedish astronomer Anders Celsius in 1742. It attained the name of centigrade because of its 100-degree interval between the specified points. Celsius is the easiest scale to use and fortunately to convert Celsius to Fahrenheit is also pretty simple:

°C to °F formula: Multiply by 9, divide by 5, and add 32.

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B. Fahrenheit

Based on 32 degrees for the freezing point, and 212 degrees for the boiling point of water, this temperature scale was invented in 1724 by the German physicist Daniel Gabriel Fahrenheit. The average temperature of a human body is 98.6°F, while the absolute zero is -459.67°F on Fahrenheit.

The interval between the two points is split up into 180 equal parts. To convert degree Fahrenheit into Celsius, here is the formula:

°F to °C: Subtract 32, multiply by 5, and divide by 9.

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C. Kelvin

Named after the British physicist William Thomson Kelvin, this temperature scale was proposed in 1848. It is an absolute temperature scale, with absolute zero below which temperatures do not exist. This also suggests that there are no negative numbers on this scale since the lowest number is 0 K.

Absolute zero however cannot technically be achieved. It is the point where molecules would stop moving – it is thereby “infinitely cold.”

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Solved Examples


Convert 40° Celsius (an extremely warm day) to Fahrenheit



Since, the temperature measuring scales begin at a different number (0 vs. 32), so we will require adding or subtracting 32

Given that the scales rise at a different rate (100 vs 180), so we will also require multiplying

And thus, to convert:

  • from Celsius to Fahrenheit: we need to first multiply by  180/100 [9/5], then add 32

  • from Fahrenheit to Celsius: first subtract 32, then multiply by 100/ 180 [5/9]

We simplified 180 and100 to 9 and 5

Now, Using convert Celsius to Fahrenheit formula: 9/5 × °C + 32


First: Divide 40° / 5 = 8

Then: Multiply 8 × 9 = 72

Then: 72 + 32 = 104° F



How to Convert 75° Celsius into Kelvin (k)? Also, find Fahrenheit.


Using conversion formula for Celsius to Kelvin, we get

75°C + 273.15 = 348.15K

For converting Kelvin into Fahrenheit, the formula is:

(K − 273.15) × 9/5 + 32 = °F.

This means (348.15 - 273.15) × 9/5 + 32 = 167 °F

Note: You can also take the substitution value of 9/5 (i.e. 1.8)

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Fun Facts

  • Celsius scale is used throughout the world, except for the United States

  • The hottest temperature that’s recorded on planet Earth is 57.8°C / 136°F, in Lybia, on September 13, 1922.

  • The coldest temperature that’s recorded on Earth is -89.2°C / -128.6°F, Antarctica on July 21, 1983.

  • One of the hottest temperatures ever recorded was 56.7°C / 134°F, in Death Valley, US on July 10, 1913.

  • The highest temperature ever recorded in New Zealand was 42.4°C / 108.3°F, on February 7, 1973.

  • The coldest temperature ever recorded is -24°C / -11°F, in Morocco, Africa on February 11, 1935

  • The originator of the Kelvin scale also chronicled the 2nd law of thermodynamics, which communicates that heat will not flow from a colder body to a hotter body.

FAQ (Frequently Asked Questions)

Q1. Why is Temperature Conversion Required?

The three measuring scales are appropriate ways of recording temperatures and they all can be extracted from one another through formulas since they are linked to each other. There are mainly two temperature scales that are used worldwide.

  • °C, the Celsius Scale (component of the Metric System, used in most countries)

  • °F, the Fahrenheit Scale (used primarily in the US), and

Remember that the Kelvin scale is often used by engineers. It is not absolutely a temperature scale but it also has a Rankine temperature scale which is commonly used in engineering systems where heat calculations are done using °Fahrenheit.

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Q2. What is the Technology of Mercury Thermometers?

Not long ago, thermometers used to be infused with mercury inside the glass. If the temperature got hotter, the mercury rose and moved up through the thin duct. We could observe what the volume of temperature was by noting it off the scale of numbers on the thermometer duct. However, mercury appeared to be toxic and it was soon replaced with different liquids.

The concept still remains the same irrespective, as the temperature goes up, the liquid enlarges and rises, and when the temperature moves down, the liquid contracts and drops down the duct.

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