Which Is Colder: Minus 40°C Or Minus 40°F?

 Science can feel confusing at times and a relevant example is the doubts associated with temperature readings in Celsius and Fahrenheit

While most of the world uses the Celsius system for measuring temperature, you might sometimes come across readings mentioned in Fahrenheit. In this context, a question often asked is which is colder: minus 40°C or minus 40°F? If you are not aware of the basic working of Celsius and Fahrenheit, you are likely to answer this incorrectly. Let's check out the fundamentals to understand and solve this puzzle.

Which is colder: minus 40°C or minus 40°F?

Depending on how you perceive this query, you might either go with minus 40°C or the minus 40°F to be colder. However, you will be surprised to know that minus 40° Celsius and minus 40° Fahrenheit are exactly the same temperature. There is no difference between minus 40°C and minus 40°F. For scientific proof, we can simply look at the formula for converting Celsius to Fahrenheit and vice-versa.

°F = (°C × 9/5) + 32

If we put -40°C in the above formula:

°F = (-40 × 9/5) + 32

= (-72) + 32

= -40°F

You can also apply this in the reverse manner, and the result will still be the same. Below is the illustration.

°C = (°F - 32) × 5/9

°C = (-40 - 32) × 5/9

= (-72) × 5/9

= -360/9

= -40°C

As is evident, minus 40 degree Celsius is exactly the same temperature as minus 40 degree Fahrenheit.

Why minus 40 degree Celsius is the same as minus 40 degree Fahrenheit?

The mathematical equations have clearly illustrated that both are referring to the same temperature. But the next question you may ask is why this is happening. To understand that, we have to look at how the Celsius and Fahrenheit readings are formulated.

In the case of Celsius system, the 0 reading is taken as the temperature of freezing water. The boiling water temperature is measured at 100 degree Celsius. We can consider this as a physical scale of a particular length. In the case of Fahrenheit system, 32 degrees is set as the freezing point of water, whereas 212 degrees is taken as the boiling point of water.

If we compare the two scales, the Fahrenheit system has smaller divisions, whereas the Celsius system has longer divisions. If we consider these as two scales and put them side by side, the -40° Celsius and the -40° Fahrenheit is where the two systems converge. It is the only point where these two systems converge. All other similar readings would be referring to a different temperature.

How to easily remember and not get confused?

People may need more time to comprehend this surprising aspect of -40 degree Celsius and -40 degree Fahrenheit. Another easy way to understand this is to consider Celsius and Fahrenheit as two racers. The Celsius is at 0-meter mark and has longer strides. In comparison, Fahrenheit is already ahead at 32 meters, but has smaller 0.55-meter steps.

Since Celsius is taking longer strides, it will eventually catch up with Fahrenheit at some point in the race. The minus 40 degree is exactly that point where the two racers meet. Below is an easy way to remember, as to what actually is happening.

Below -40, Celsius numbers are colder than the same Fahrenheit number.

Example: -50°C is colder than -50°F.

Above -40, Fahrenheit numbers are colder than the same Celsius number.

Example: -20°F is colder than -20°C.

But at exactly -40, they are identical.