Calculate pipe flow rate, water velocity, gallons per minute, gallons per hour, pipe area, pressure drop, head loss, and friction loss. Use this pipe flow calculator for plumbing lines, water supply pipes, irrigation piping, drainage planning, and general pipe sizing estimates.
Diameter and velocity:
The calculator finds pipe area from the inside diameter, then multiplies area by water velocity to estimate flow rate.
Diameter and pressure drop:
The calculator uses a Hazen-Williams style estimate to approximate water flow based on pipe diameter, pipe length, roughness, and available pressure drop.
Known flow rate:
Enter a known flow rate to estimate water velocity, pipe capacity, and pressure loss through the pipe.
A pipe flow calculator helps estimate whether a pipe can carry the needed water flow without excessive velocity or pressure loss.
It can help compare gallons per minute, gallons per hour, pipe velocity, pipe area, friction loss, pressure drop, and capacity for plumbing, irrigation, and water supply planning.
Your result shows estimated flow rate, water velocity, pipe area, pipe volume, pressure loss, head loss, friction loss per 100 feet, and available flow capacity. These are planning estimates only. Actual flow can change based on fittings, valves, elbows, pipe age, elevation change, water temperature, pump performance, and local plumbing code requirements.
Calculate the inside pipe area, then multiply that area by water velocity. The result can be converted into gallons per minute.
Many plumbing estimates try to keep water velocity in a moderate range to reduce noise, friction loss, and wear. Very high velocity can increase pressure loss and water hammer risk.
Yes. Longer pipe runs usually increase friction loss, which can reduce available flow at the fixture or outlet.
No. This calculator gives an estimate. Real systems can be affected by elbows, valves, fittings, elevation, pumps, pipe condition, water temperature, and code requirements.