Estimate Your Horsepower!
(THIS IS JUST AN ESTIMATE BASED ON SIMPLE CALCULATIONS!)
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*.
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*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*.
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*Note: Assuming a 20% drive train loss.
Convert P-Metric tire to Tire Diameter inches
Example: 195/75R15
/
R
Tire Diameter:
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.
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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 Rear End Gear Ratio
Enter the tire diameter in inches, rpm's of the motor at a certain speed as indicated by your speedometer in mph. This calculation assumes the car's transmission is in drive or 1:1 ratio, no overdrive.
Tire Diameter (in)
RPM
Speed at RPM (mph)
Rear End Gear Ratio
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