# Hydraulic Oil Pumps - Horsepower Required

## Horsepower required by hydraulic pumps

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A practical formula for calculating horsepower required by a hydraulic pump

can be expressed as

P_{HP}= q p / 1714 (1)

where

P_{HP }= horsepower (HP)

q = required pump capacity (gpm)

p = required pressure (psi)

*1 gpm (US) =6.30888x10*^{-5}m^{3}/s = 0.227 m^{3}/h = 0.06309 dm^{3}(litre)/s = 2.228x10^{-3}ft^{3}/s = 0.1337 ft^{3}/min = 0.8327 gpm (UK)*1 psi (lb/in*^{2}) = 144 psf (lb_{f}/ft^{2}) = 6,894.8 Pa (N/m^{2}) = 6.895x10^{-3}N/mm^{2}= 6.895x10^{-2}bar*1 hp = 745.7 W*

### Example - Hydraulic Pump

Power required by a a pump with *20 gpm* capacity and *1500 psi * pressure can be calculated as

P_{HP}= (20 gpm) (1500 psi) / 1714

= 17.5 HP

### Efficiency

Note that the equation above can be used for a *100%* efficient pump - which in the practial life is never true. An overall efficiency of *80 - 95%* is common.

The equation above *(1)* can be modified to

*P _{HP} = q p / ((μ / 100) 1714) (2)*

*where *

*μ* = overall efficiency (%)

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