IMPERIAL
The horsepower required to overcome air resistance is the speed in miles per hour, cubed, times the frontal area in square feet divided by 150,000
![1](https://de.webtec.com/api/i.aspx?wteqi23a.gif;93;35)
Where:
MPH = Speed in miles per hour
FA = Frontal area in square feet
HP = Horsepower
150,000 = A conversion constant
Example:
What is the horsepower required to overcome air resistance of a vehicle travelling 40 miles per hour and having a frontal area of 80 square feet?
![2](https://de.webtec.com/api/i.aspx?wteqi23b.gif;83;51)
METRIC
The power in watts required to overcome air resistance is the speed in kilometres per hour, cubed, times the frontal area in square metres divided by 77.86
![1](https://de.webtec.com/api/i.aspx?wteqm23a.gif;82;33)
Where:
MPH = Speed in kilometres per hour
FA = Frontal area in square metres
P = Power in Watts
77.86 = A conversion constant
Example:
What is the power in watts required to overcome air resistance of a vehicle travelling 65 kilometres per hour and having a frontal area of 7.5 m2?
![4](https://de.webtec.com/api/i.aspx?wteqm23b.gif;99;49)