The formula for calculating wind chill in Fahrenheit is:
Windchill = 35.74 + 0.6215T - 35.75 x V^0.16 + 0.4275T x V^0.16.
"T" stands for temperature and "V" is the wind speed.
Raise the wind speed to the 0.16 power. For example, if the wind speed is 20 miles per hour, you get 1.615.
Multiply the result from Step 2 by -35.75. In this example, you would multiply 1.615 by -35.75, which equals -57.74.
Multiply the result from Step 2 by the temperature and 0.4275. Assuming the temperature is 10 degrees Fahrenheit, you would multiply 10 times 0.4275 times 1.615 to get 6.904.
Multiply the temperature by 0.6215. In this example, you would multiply 0.6215 times 10 to get 6.215.
Take the sum of the results from steps 3 through 5. In this example, you would add -57.74 plus 6.904 plus 6.215 to get a total of -44.621.
Add 35.74 to the result from step 6 to calculate the windchill. Finishing this example, you would add 35.74 to -44.621 to find the windchill equals -8.88 degrees Fahrenheit.