How to Convert Celsius to Fahrenheit

You might not have thought it necessary to convert temperature from one unit to the other just because tons of digital instruments can do this anyway. With digital thermometers and your smart devices, you didn’t need to bother yourself with the mundane task of converting Degrees Celsius to Degrees Fahrenheit.

For those living in countries that have adopted the Metric System decades ago, it seems hardly necessary to make any conversion.  It is simple enough to continue recording all temperatures as Degrees Celsius without any thought of what it means in Degrees Fahrenheit.

It has not always been like that:

Degrees Fahrenheit

Before Degrees Celsius was widely used, the primary temperature unit was Degrees Fahrenheit. Denoted with the symbol °F, this unit of measuring temperature is defined as two fixed points: the freezing temperature of water at 32°F, and the temperature at which water boils at 212°F. These temperatures are measured at sea level and with the standard atmospheric pressure. The space between these two points is split into 180 equal parts.

Way back in 1724, a German physicist by the name of Daniel Gabriel Fahrenheit developed the unit of measuring temperature named after him. To arrive at his definition for hot and cold temperatures, he at first used a scale that featured an equal amount of ice-salt mixture. He selected 30°F as the point where water freezes and 90°F as the average temperature of the human body. Later he tweaked the scale to show 32°F as the point where snow melts and 96°F as the normal temperature of the human body.

As the reference to water’s boiling and freezing points became more widely accepted he again adjusted his scale to enable 180 degrees to separate the boiling and the freezing points on the thermometer. This adjustment meant that 98°F and not 96°F was accepted as the normal human body temperature.

Currently, most countries no longer use Degrees Fahrenheit as the official unit of measuring temperatures.  Only a few countries, including the United States of America which did not adopt the Metric System, still use Degrees Fahrenheit to measure temperature.

Degrees Celsius

Degrees Celsius, on the other hand, which is denoted by the symbol °C is a derived unit of measuring temperature within the International System of Units.  It is based on the absolute zero (that is -273.15 °C), and the three-part water standard termed the Vienna Standard Mean Ocean Water (VSMOW). The Celsius scale (also equated with the Kelvin scale) was adopted from 1743 until 1954.  During that period the points 0 °C to denote water’s freezing point and 100 °C to show its boiling point were used. These points were measured at one standard atmospheric pressure with mercury as the thermometer’s material. (Initially 0°C was used to show water’s boiling point and 100°C as the point where snow melts).

With the redefinition of Degrees Celsius in 1954 (the first definitions of boiling and freezing points were flipped on their heads) measuring temperature in Degrees Celsius became more widely accepted. It was also still based on the absolute zero (-273.15 °C) measure.

Now that we have an idea of the origins and history of both units of temperature measurement let’s dive straight into how to convert from Celsius to Fahrenheit.

Converting from Celsius to Fahrenheit

Celsius to Fahrenheit table

For those of us who are not good with numbers, this section might be a little daunting. Here is the breakdown of the formula that must be used to achieve the conversion:

The formula: F = 9/5C + 32.

Looks simple enough.  Another way of stating this formula is to write it out as F = (9/5 x C) + 32.

“F” represents Fahrenheit (the unit you want to convert to), and “C” represents Celsius (the unit you want to convert from).


But, what is 9/5?


The above is the fraction you must use to multiply the value of the temperature in Degrees Celsius. You might say this is the factor needed to start the conversion process. Another way to express this fraction in decimals is 1.8 (which is merely the result of nine divided by five which is less than two times.)

So, you might see this temperature conversion formula presented in other texts as F = 1.8 C + 32. Rest assured, it means the same thing.

Finally, add the number 32 to the results of your previous multiplication effort.

But, why would you need to add this number?

It so happens that 32 °F represents the same temperature as 0°C. It is, therefore, necessary to account for this whenever you convert from Celsius to Fahrenheit.

To recap:

Converting from Degrees Celsius to Degrees Fahrenheit needs two steps.

Step one – multiply the Celsius temp by 1.8 (the same thing as 9/5 remember)

Step two – add the result to 32.

Here is an example of this:

Converting 25 °C to °F:
25 °C = 25 × 1.8 + 32 = 77 °F

With a further show of working, it would go like this:

25 °C = 25 × 1.8 = 45

45 + 32 = 77 °F

So, from the example above, 25 °C is equal to 77 °F.

You can have fun using this simple formula to convert any temperature expressed in Degrees Celsius into Degrees Fahrenheit.  Of course, if you want to switch back to Degrees Celsius, the formula can be used with one significant difference – rather than adding 32 to the result, you would need to subtract it instead.

Converting without a calculator

What if you don’t need to do an exact conversion and all you need is a rough estimate? This situation may be quite relevant if you do a lot of cooking and need only to do quick conversions without bursting your brain cells and using a calculator.

Here is an alternative approach in this case:

To convert from Celsius to Fahrenheit multiply the Celsius temperature by 2.  Add 30 to the result.

With this rough method, you can easily convert 25 °C to °F.

Here goes:

25 x 2 = 50

50 + 30 = 80

So, by the above working, the rough estimate provided by your quick (mental) conversion is that 25 °C  is roughly around 80°F.  Not too far off from the more accurate calculation of  77°F we worked out earlier.

Things to Remember

Are you comfortable doing temperature conversions on your own? Once you know the formula to use, it becomes a no-brainer.  You can efficiently practice using it to good effect and even impress your friends and associates on your mathematical prowess.

  • It is important to remember that you need to take the two steps required to make the conversion. Multiply then add. If you try to do it the other way around (add then multiply) you will only succeed in messing things up.
  • Also, ensure that you are converting from Celsius to Fahrenheit. So, the thermometer should first give you a reading in Degrees Celsius.  The temperature is what you would then need to convert.
  • Also, you must use the multiplier (9/5 or 1.8 which both means the same thing).  No other figure will do the job. If you forget to multiply the temperature by this fraction (decimal), you won’t get a correct answer even if you remembered to add the number 32 to that amount.  In fact, such a result will always be lower than the right answer!
  • Of course, also remember to add the number 32 to the result you get. This figure is the number you must add and no other value.  As mentioned earlier, this number in Fahrenheit represents the temperature of water at zero degrees Celsius.
  • If you are in a pinch and need a quick, easy to remember formula to give you a rough estimate, you have it in the formula steps “multiply by two then add 30”. This approach provides a quick solution in the event you are cooking and need a rapid temperature check in Fahrenheit instead of Degrees Celsius.

Final Conclusion

There might be times when you need to convert temperature from Degrees Celsius to Degrees Fahrenheit quickly.  While it is possible to use digital thermometers and smart devices to accomplish this, you might not always have these convenient tools around. If you must do so without help from digital instruments, a simple mathematical formula comes to the rescue.

It is not a complicated formula to remember, and it involves two easy steps to convert any Celsius temperature to temp in Fahrenheit. In a pinch, you can also use a simple formula to arrive at a rough estimate of the temperature conversion without much cranial stress.

Most of all, it is easy and fun to do this simple temperature conversion on your own.

Of course, if you don’t care too much about working this conversion yourself, you can take comfort in your knowledge of how to do it. You also won’t have trouble understanding what is involved whenever you come across examples of temperatures that were converted from Celsius to Fahrenheit.

  • July 12, 2018
  • Blog
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