🔧Plumbing

Pipe Sizing Calculator

Determine the correct pipe diameter based on flow rate, pressure, material, and run length.

Calculate Pipe Size

Flow Rate (GPM)

Pipe Material

Total Run Length (ft)

Max Velocity (fps)

Pipe Sizing Fundamentals

Correct pipe sizing balances flow velocity, pressure drop, and cost. Too small a pipe causes high velocity (noise, erosion, excessive pressure loss). Too large wastes material and money.

Velocity Guidelines

Residential (quiet): 4–5 fps recommended to minimize water hammer and noise.
Standard: 5–8 fps is the most common design range.
Commercial: Up to 10 fps acceptable for main supply lines.
Never exceed 10 fps to prevent erosion and excessive noise.

Material Considerations

PEX and PVC have smoother interiors (higher C-factor) resulting in less friction than copper. However, copper is more rigid and better suited for exposed runs. CPVC handles hot water better than PVC but has a slightly smaller internal diameter than PVC at the same nominal size.