# Brake Horsepower

Written by Jerry Ratzlaff on . Posted in Fluid Dynamics

Brake horsepower, abbreviated as BPH, is the engine's horsepower required to overcome the loss in power caused by the pump.

## Brake Horsepower formulas

 $$\large{ BHP = \frac{ 100 \; Q \; h_t }{ 3960 \; \eta } }$$ $$\large{ BHP = \frac{ Q \; h_t \; SG }{ 3960 \; \eta } }$$ $$\large{ BHP = \frac{ \tau \; RPM }{ 5252 } }$$ $$\large{ BHP = \frac{ WHP }{ \eta_p } }$$

### Where:

 Units English Metric $$\large{ BHP }$$ = brake horsepower $$\large{\frac{lbf-ft}{sec}}$$ $$\large{\frac{Btu}{s}}$$ $$\large{ Q }$$ = flow rate $$\large{\frac{ft^3}{sec}}$$ $$\large{\frac{m^3}{s}}$$ $$\large{ \eta_{tp} }$$  (Greek symbo; eta) = efficiency dimensionless $$\large{ \eta_p }$$  (Greek symbol eta) = pump efficiency dimensionless $$\large{ RPM }$$ = revolutions per minute $$\large{\frac{rev}{min}}$$ $$\large{\frac{rev}{min}}$$ $$\large{ \tau }$$  (Greek symbol tau) = torque $$lbf-ft$$ $$N-m$$ $$\large{ h_t }$$ = total head $$ft$$ $$m$$ $$\large{ SG }$$ = specific gravity dimensionless $$\large{ WHP }$$ = water horsepower $$\large{\frac{lbf-ft}{sec}}$$ $$\large{\frac{Btu}{s}}$$ 