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Fixture units → GPM
Convert water-supply fixture units (WSFU) to peak demand GPM via the classic Hunter's Curve. Pick the right curve (predominantly flush-tank vs flush-valve) for your system type.
Peak demand
67.5 GPM
50 WSFU on the flush-valve curve.
Hunter's Curve is a probabilistic peak-demand estimate. For final design, the plumbing engineer reconciles WSFU per fixture (IPC Tables 604 / 709), diversity, and continuous loads.
Hunter's Curve background
R.B. Hunter's 1940 NIST study established the empirical relationship between WSFU and probable peak GPM that still underpins IPC Appendix E demand sizing. Two curves shipped: predominantly flush-tank (residential / office) and predominantly flush-valve (institutional / heavy commercial). This tool approximates both via a log-linear fit to the published values.
Built by Forward
Forward runs fixture-unit conversion, pipe-size-for-gpm, drain-pipe sizing for DFU, water-heater sizing, plus the broader NEC + IBC + IMC calcs and project lookups against Procore + Autodesk + OneDrive.