# Resources

Hydraulic Motors Calculations Guide:

## GPM of Flow Needed for Fluid Motor Speed:

Motor Displacement x Motor RPM ÷ 231

Example: How many GPM are needed to drive a 3.75 cubic inch motor at 1500 rpm

Motor Displacement = 3.75 cubic inches per revolution
Motor RPM = 1500
Motor Displacement x Motor RPM ÷ 231 = 3.75 x 1500 ÷ 231 = 24.35 gpm

## Fluid Motor Speed from GPM Input:

231 x GPM ÷ Fluid Motor Displacement

Example: How fast will a 0.75 cubic inch motor turn with 6 gpm input?

GPM = 6
Motor Displacement = 0.75 cubic inches per revolution
231 x GPM ÷ Fluid Motor Displacement = 231 x 6 ÷ 0.75 = 1,848 rpm

## Fluid Motor Torque from Pressure and Displacement:

PSI x Motor Displacement ÷ (2 x π)

Example: How much torque does a 2.5 cubic inch motor develop at 2,000 psi?

Pressure = 2,000 psi
Motor Displacement = 2.5 cubic inches per revolution
PSI x Motor Displacement ÷ (2 x π) = 2,000 x 2.5 ÷ 6.28 = 796.19 inch pounds

## Fluid Motor Torque from Horsepower and RPM:

Horsepower x 63025 ÷ RPM

Example: How much torque is developed by a motor at 12 horsepower and 1750 rpm?

Horsepower = 12
RPM = 1750
Horsepower x 63025 ÷ RPM = 12 x 63025 ÷ 1750 = 432.17 inch pound

## Fluid Motor Torque from GPM, PSI and RPM:

GPM x PSI x 36.77 ÷ RPM

Example: How much torque does a motor develop at 1,200 psi, 1500 rpm, with 10 gpm
input?

GPM = 10
PSI = 1,500
RPM = 1200
GPM x PSI x 36.7 ÷ RPM = 10 x 1,500 x 36.7 ÷ 1200 = 458.75 inch pounds second

Unit Conversion Guide:

To ConvertIntoMultiply By
BarPSI14.5
ccCu. In.0.06102
°C°F(°C x 1.8) + 3
Kglbs.2.205
KWHP1.341
LitersGallons0.2642
mmInches0.03937
Nmlb.-ft0.7375
Cu. In.cc16.39
°F°C(°F – 32) ÷ 1
GallonsLiters3.785
HPKW0.7457
Inchmm25.4
lbs.Kg0.4535
lb.-ft.Nm1.356
PSIBar0.06896
In. of HGPSI0.4912
In. of H20PSI0.03613
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