Free Pipe Sizing Calculator
Determine the minimum pipe diameter required for a given flow rate and maximum velocity.
GPM
ft/s
Minimum Diameter
1.17 in
Cross-Section Area1.069 sq in
Minimum Diameter vs Required Flow
Pipe Sizing
Rearrange the continuity equation Q = A x V to solve for the minimum cross-sectional area, then back-calculate the diameter.
D = 2 x sqrt( Q / (V x pi) )
Always round up to the next standard pipe size available from your supplier.
Example Calculation
Need 20 GPM at a maximum velocity of 6 ft/s.
- 01Q = 20 / 448.831 = 0.04456 cu ft/s
- 02A = 0.04456 / 6 = 0.007427 sq ft
- 03D = 2 x sqrt(0.007427 / pi) x 12 = 1.17 in
- 04Choose the next standard size: 1-1/4 inch pipe.
Frequently Asked Questions
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