Converting Fahrenheit to Celsius
Fahrenheit and Celsius are two distinct but widely used temperature scales. The unit of measure for Fahrenheit is written using the degree Fahrenheit symbol (°F), whereas the unit for Celsius is denoted by the degree Celsius symbol (°C).
Fahrenheit is the most commonly used temperature measurement in the United States. However, if you travel to other countries, you will notice that Celsius is more commonly used. Therefore, learning how to convert temperatures between the two scales can help you understand what kind of temperature is being discussed no matter where you are in the world.
How to Convert from Fahrenheit to Celsius
When converting from Fahrenheit to Celsius, we use the following standard formula:
If we take a closer look at the formula, below are the steps to convert a given Fahrenheit temperature to Celsius.
- Subtract [latex]{32}[/latex] from the given Fahrenheit temperature (simplify operations that are inside the parenthesis first)
- Multiply the difference by [latex]\Large{5 \over 9}[/latex]
- Express or write the answer with the degrees Celsius symbol (°C)
Alternate Method (°F to °C)
Another formula that we can use as an alternative to convert temperatures from the Fahrenheit scale to the Celsius scale is dividing the quantity [latex]\left( {^\circ F – 32} \right)[/latex] by [latex]\textbf{{1.8}}[/latex]. But you might ask, how did we get this alternate method?
Well, multiplying the quantity [latex]\left( {^\circ F – 32} \right)[/latex] by [latex]\Large{5 \over 9}[/latex]
[latex]{\Large{5 \over 9}}\left( {^\circ F – 32} \right)[/latex]
is equivalent to dividing the quantity [latex]\left( {^\circ F – 32} \right)[/latex] by [latex]\Large{9 \over 5}[/latex]. Notice that the numerator and denominator have switched.
[latex]\Large{{\left( {^\circ F – 32} \right)} \over {\large{{9 \over 5}}}}[/latex]
Since [latex]{\Large{9 \over 5}} = 1.8[/latex], we have the alternate formula:
Now, let’s convert 86° Fahrenheit to degrees Celsius using both formulas to see if we get the same answer.
And we did! Using both formulas, we get the same answer of 30° C. Therefore, we can say that 86 degrees Fahrenheit is 30 degrees Celsius.
Converting Temperatures from Fahrenheit to Celsius Examples
There is no such thing as too much practice. For a better understanding of the formulas and steps involved in Fahrenheit to Celsius conversion, let’s go through a few examples.
Example 1: Convert 140° F to °C.
For this first example, we’ll use the standard formula for converting temperature to the Celsius scale.
Answer: 140 degrees Fahrenheit is 60 degrees Celsius OR 140° F = 60° C.
Example 2: What is 96.8 degrees Fahrenheit in Celsius?
The Fahrenheit temperature in this example contains a decimal. Will it also have a decimal once converted to the Celsius scale? Let’s find out.
Using the alternative formula, we have
Our answer came up as a whole number. Therefore, just because a Fahrenheit temperature has a decimal, it does not mean that the corresponding Celsius temperature will also have a decimal.
Answer: 36° C
Example 3: Convert -13° F to °C.
Sometimes, you’ll also be given temperatures in the negatives. This is common especially if you’re talking about very cold or below freezing temperatures. However, as long as you know the formula, converting them from Fahrenheit to Celsius is easy.
Answer: -13 degrees Fahrenheit is -25 degrees Celsius OR -13° F = -25° C.
Example 4: The normal body temperature of a cheetah is at 101° F. After sprinting during a hunt, its body temperature increased 1.2° F. What was its increased body temperature in Celsius?
Before we do any conversion, we first need to find out the cheetah’s increased body temperature in Fahrenheit. We’ll do so by adding 1.2° F to it’s normal body temperature.
- Cheetah’s Normal Body Temperature: 101° F
- Cheetah’s Body Temperature After Sprinting: 101° + 1.2° = 102.2° F
Now that we know it’s increased body temperature in Fahrenheit, we can proceed with converting 102.2° F to Celsius. We’ll use the alternative formula for this one.
Answer: The cheetah’s increased body temperature was 39° C.
Example 5: When I woke up on Christmas morning last year, the temperature outside was 25° F. By dinner time, the outside temperature has decreased by 6° F. What was the decreased temperature in Celsius?
First, we need to get the decreased temperature in Fahrenheit.
- Morning Outside Temperature: 25° F
- Dinner Time Outside Temperature: 25° – 6° = 19° F
Next, let’s find out what 19° F is in Celsius using the Fahrenheit to Celsius conversion formula.
Answer: It was about -7.2° C outside by dinner time on Christmas day last year.
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Converting Fahrenheit to Celsius Practice Problems with Answers