Estimate water used generally from flow rate and run time.
Water used = flow rate × run time. Typical showerheads run ~2 gal/min and low-flow models ~1.5; garden hoses run far more.
Gallons
gallons = flow (gal/min) × minutes
Flow estimate only.
It is a flow estimate — meters also include leakage and other draws.
Rates are approximate reference values. Local rates, exemptions and rules can differ, so treat the output as a planning figure only.