Energy Loss Calculator

Hydraulic power dissipated by head loss: P_loss = ρgQh_f. Also computes specific energy loss and pressure equivalent.

Fluid Mechanics II

Common fluids — click to auto-fill density

Inputs

Head loss hf (m)

Total head loss — include both major (friction) and minor losses.

Volumetric flow rate Q (L/s)

Fluid density ρ (kg/m³)

Theory

Hydraulic power loss (rate of energy dissipation):

P_loss = ρ × g × Q × h_f [W]

P_loss = ṁ × g × h_f = ṁ × e

Four equivalent forms of the same loss:

Form	Symbol	Formula	Units
Head	h_f	given	m
Specific energy	e	g × h_f	J/kg
Pressure	ΔP	ρg × h_f	Pa
Power	P_loss	ρgQ × h_f	W

Where:

P_loss = hydraulic power loss (rate of energy dissipation) [W]
ρ = fluid density [kg/m³]
g = gravitational acceleration = 9.81 m/s²
Q = volumetric flow rate [m³/s]
h_f = total head loss (friction + minor losses) [m]
ṁ = mass flow rate = ρQ [kg/s]
e = specific energy loss = g × h_f [J/kg]

P_loss represents the mechanical energy dissipated as heat per second. It equals the pump power required to sustain a flow against that head loss at 100% efficiency. Doubling flow rate doubles the loss; doubling head loss also doubles it.