About the Fluid Flow Calculator

Continuity gives Q = v × A: flow is velocity times the pipe's cross-section. A 1-inch pipe (0.785 in² = 0.00545 ft²) at 5 ft/s delivers 0.0273 ft³/s — about 12.2 GPM. Doubling the diameter quadruples the area, so the same velocity moves four times the water.

Laminar vs Turbulent

The Reynolds number separates the two regimes: Re = v·D/ν. Below 2,300, flow is smooth and predictable (lubrication, blood, microfluidics); above 4,000, turbulence mixes the fluid and sharply increases friction losses — which is why pipe sizing rules keep domestic water flow in the turbulent-but-manageable range.