What Temperature Does Fahrenheit Equal Celsius?

Temperature at Which Fahrenheit and Celsius Are the Same

This thermometer displays the Fahrenheit and Celsius temperature scales. The temperatures are the same at -40 degrees.
This thermometer displays the Fahrenheit and Celsius temperature scales. The temperatures are the same at -40 degrees. Andrew Johnson / Getty Images

Question: What Temperature Does Fahrenheit Equal Celsius?

There is one point on the Fahrenheit and Celsius scales where the temperatures in degrees are equal. This is -40 °C and -40 °F. If you can't remember the number, there is a simple algebraic method to find the answer.

Answer: Rather than converting one temperature to another (not helpful because it assumes you already know the answer), you set degrees Celsius and degrees Fahrenheit equal to each other using the conversion formula between the two temperature scales:

°F = (°C * 9/5) + 32
°C = (°F - 32) * 5/9

It does not matter which equation you use. Simple use "x" instead of degrees Celsius and Fahrenheit. You can solve this problem by solving for x:

°C = 5/9 * (°F - 32)
x = 5/9 * (x - 32)
x = (5/9)x - 17.778
1x - (5/9)x = -17.778
0.444x = -17.778
x = -40 degrees Celsius or Fahrenheit

Working using the other equation:

°F = (°C * 9/5) + 32
°x - (°x * 9/5) = 32
-4/5 * °x = 32
°x = -32 * 5/4
x = -40°

More About Temperature

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How To Convert Celsius To Fahrenheit
Celsius Versus Centigrade
The Fahrenheit Scale