Piping Pressure Drop - HVAC Calculator Toolbox

About this calculator This calculator determines the total pressure drop through a piping system including straight runs, fittings, and elevation changes. Use it when sizing pumps or verifying that available pump head is sufficient for a hydronic heating or cooling loop. The calculation converts fittings to equivalent length and applies standard friction loss rates.

Use when You need to calculate total pressure loss through a piping system.

Formula ΔP = Vertical Rise × 0.43 + Equivalent Length × Loss/ft

Variables

Vertical Rise Vertical rise in feetVertical Drop Vertical drop in feetHorizontal Pipe Horizontal pipe run in feetFittings Eq. Length Equivalent length of fittings in feetPressure Loss/ft Friction loss rate in PSI per footGPM Flow rate in gallons per minute

Vertical Rise (ft)

Upward pipe distance in feet (0.43 PSI/ft)

Vertical Drop (ft)

Downward pipe distance in feet

Horizontal Pipe (ft)

Horizontal run length in feet

Fittings Eq. Length (ft)

Total equivalent length of fittings

Pressure Loss (PSI/ft)

Friction loss rate per foot of pipe

GPM

Gallons per minute flow rate

Vertical Loss (PSI) —

Horizontal Loss (PSI) —

Total Drop (PSI) —

How is piping pressure drop calculated?

Piping pressure drop is the total loss in fluid pressure as water flows through a hydronic heating or cooling system. It includes friction losses in straight pipe runs, losses through fittings and valves (expressed as equivalent pipe lengths), and static head from elevation changes. The friction loss per unit length depends on flow rate, pipe diameter, pipe material roughness, and fluid properties. For closed hydronic loops, the pump must overcome only the friction losses because the static head cancels out in a closed circuit. For open systems such as cooling towers, the pump must also overcome the elevation difference. Total pressure drop is typically expressed in feet of head or PSI: ΔP (PSI) = vertical rise × 0.433 + equivalent length × friction rate per foot. Pump selection requires matching the pump curve to the system's total pressure drop at the design flow rate.

Related Calculators