Horsepower Calculator

Do you know where horse power came from? FYI: 1 HP=330 lbs of coal pulled vertically 100' within 1 minutes time. James Watt was trying to design a steam powered engine to replace a team of 2 horses to lift coal out of a mine. This became the US standard for measuring power. Also, 745 watts = 1 HP. The typical 120VAC home outlet can supply up to about 1,500 watts, or about 2 HP.

Calculate HP from Trap Speed
Vehicle weight in pounds (including driver) lbs	Trap speed at end of 1/4 mi in m.p.h. m.p.h.
*You are making : HP at the rear wheels and HP at the flywheel.** JavaScript must be enabled in your browser for the calculation to work.

*Note: Assuming a 20% drive train loss.

Calculate HP from ET
Vehicle weight in pounds (including driver) lbs	ET in seconds sec
*You are making : HP at the rear wheels and HP at the flywheel.** JavaScript must be enabled in your browser for the calculation to work.

*Note: Assuming a 20% drive train loss.

Calculate mph for RPM range
Tire diameter		Gear Ratio
This calculation assumes the car's transmission is in drive or 1:1 ratio, no overdrive. For Overdrive cars mutliply the overdrive ratio times the rear and gear ratio. Example a 700R4 transmission has an overdive ratio 0.7:1. For a 4.11 rear end multiply 4.11 x 0.7 = 2.877. Enter 2.877 as the number for the gear ratio to calculate speeds in overdive. JavaScript must be enabled in your browser for the calculation to work.
1000 rpm	mph	4500 rpm	mph
1500 rpm	mph	5000 rpm	mph
2000 rpm	mph	5500 rpm	mph
2500 rpm	mph	6000 rpm	mph
3000 rpm	mph	6500 rpm	mph
3500 rpm	mph	7000 rpm	mph
4000 rpm	mph	7500 rpm	mph

Calculate Horsepower From Trap Speed	Calculate Horsepower From ET
Calculate Tire Diameter	Calculate MPH for RPM Range
Calculate Rear End Gear Ratio