Columns with a yellow background are output.
Fill in all other columns and click the "Calculate" button to use.

Finding Horsepower with Weight and Trap Speed.
Vehicle
Weight (lbs)
1/4 Mile
Trap MPH
Your Estimated
Horsepower

Finding Horsepower from Torque and RPM.
Torque
(ft-lbs)
RPM
HP

Finding ET and MPH with Weight and Horsepower.
Vehicle
Weight (lbs)
Horse-
Power
Estimated
E.T
Trap
Speed

Adjusting ET for Elevation.
Old ET (s)
Elevation (ft)
New ET

Finding RPM with Gear Ratio, Speed, and Tire Size.
OD is your transmission's overdrive ratio. If you do not have overdrive, use "1". If you have overdrive, but don't know the ratio, a good guess is ".7".

Gear
Ratio
Speed
(MPH)
OD
(see above)
Tire
Diam. (in)
RPM
Alternatively, you may use this calculator if you don't know your tire diameter. Instead, enter the 3 numbers listed on the side of the tire. For example, if the tire says something like "225/50/R16", use 225 for tire width, 50 for aspect ratio, and 16 for rim diameter.

Gear
Ratio
Speed
(MPH)
OD
(see above)
Tire Width
(mm)
Aspect
Ratio
Diameter of
rim (in)
RPM

Correcting Speedometer for New Tires.
Original Tire
Diam. (in)
New Tire
Diam. (in)
Speedometer
Reading
Real
Speed
Formulas for Bore, Stroke Displacement

Finding Displacement with Bore, Stroke, and # of Cylinders
Bore
(inches)
Stroke
(inches)
# of
Cyls
Displacement (ci)
Displacement (L)

Calculate Cylinder Volume
Bore
Stroke
Cylinder Volume

Calculate Stroke
Displacement
Bore
# cylinder
Stroke
Formulas for Compression Ratio

Finding Effective Compression with Compression and Boost.
If your motor compression is 9:1, put 9 in the "motor compression" box.

Motor
Compression
Boost
(psi)
Effective
Compression

Calculate Chamber Volume
Cylinder Volume
Compression Ratio
Chamber Volume
Formulas for Fuel Requirements

Fuel Requirements in gallons per hour
This formula will calculate the approximate fuel needs for an engine based on horsepower at wide open throttle. The formula came from the Holley website. It's just a general guideline, but will get you in the ballpark. It says you should use about .5 lbs of fuel per hour per horsepower at wide open throttle.

HP@WOT
Results

Fuel Injector Requirements
  • In most cases a naturally aspirated engine will have a B.S.F.C of .50. This means that the engine will use .50 lbs. of fuel per hour for each horsepower it produces. Turbocharged engines will want to be at .60 lbs. per hour or higher.
  • Most injectors will max out at 80% duty cycle and this is the accepted industry standard.

    • HP@WOT
    BSFC
    Inj Duty Cycle
    # of Injectors
    Results lb/hour

    Max HP by injector size
  • In most cases a naturally aspirated engine will have a B.S.F.C of .50. This means that the engine will use .50 lbs. of fuel per hour for each horsepower it produces. Turbocharged engines will want to be at .60 lbs. per hour or higher.
  • Most injectors will max out at 80% duty cycle and this is the accepted industry standard.

    • Inj lb/hour
    BSFC
    Inj Duty Cycle
    # of Injs
    Results lb/hour