Water Pressure / Flow Rate Calculator

Estimate water pressure and flow rate at your fixtures based on supply pressure, pipe material, diameter, run length, and elevation change. Compare multiple pipe sizes to find the right balance of pressure and velocity.

Pipe Material

Static Pressure at Meter (PSI)

Pipe Diameter (in)

Pipe Run Length (ft)

Elevation Change (ft)

Fittings Equiv. Length (ft)

Pressure at Fixture

55.6 PSI

For 0.75" copper pipe

Max Flow Rate

231.2 GPM

C-factor = 140

Velocity

167.9 ft/s

Exceeds 8 ft/s limit

Elevation Loss

4.3 PSI

10 ft @ 0.433 PSI/ft

Pipe Diameter	Pressure @ Flow	Velocity
0.5" diameter	54.9 PSI @ 79.7 GPM	130.2 ft/s
0.75" diameter	55.6 PSI @ 231.2 GPM	167.9 ft/s
1" diameter	55.6 PSI @ 492.3 GPM	201.1 ft/s
1.25" diameter	55.7 PSI @ 884.7 GPM	231.3 ft/s
1.5" diameter	55.7 PSI @ 1428.3 GPM	259.3 ft/s
2" diameterBest value	55.7 PSI @ 3041.2 GPM	310.6 ft/s

Recommended: 2" copper pipeNone of the standard diameters maintain adequate pressure (>20 PSI) and velocity (<8 ft/s) for this run. Consider reducing the pipe run length, lowering elevation change, or installing a booster pump. The 2" pipe is the best available option.

High Velocity WarningWater velocity of 167.9 ft/s exceeds the recommended 8 ft/s maximum. High velocity causes noise (water hammer), accelerated pipe erosion, and premature fitting wear. Upsize the pipe diameter to reduce velocity.

This is a simplified estimate using Hazen-Williams methods for residential cold-water systems. Actual pressure depends on municipal supply conditions, time-of-day demand, fixture count, and pipe condition. Consult a licensed plumber for final sizing.