Flow Rate Calculator

Determine the volumetric and mass flow rate of a fluid with our flow rate calculator.

Volumetric flow rate15.708 litres a second0.015708 m³/s, 56.549 m³/h, 249 US gpm

Flow velocity2 m/s6.562 ft/s

Cross-sectional area78.5398 cm²0.00785398 m²

Per minute942.48 litres

Per hour56.5487 m³

Mass flow rate15.67969 kg/s56,446.88 kg/h, 2,074.06 pounds a minute

Momentum flux31.3594 Nthe reaction force if this jet were brought to rest

Dynamic pressure ½ρv²1.9964 kPathe pressure rise if the flow were stopped without loss

Kinetic power in the stream31.3594 W

Velocity in a 50 mm pipe8 m/s4× faster — velocity scales as the inverse SQUARE of diameter, so halving the bore quadruples the speed

Dynamic pressure there31.9424 kPa16× the original — and it goes as the FOURTH power of the diameter ratio

Velocity guidancetypicalroughly 1 to 3 m/s is the usual design range for water in pipes

The formula

Q = Av; ṁ = ρQ; continuity means A₁v₁ = A₂v₂

Velocity goes as the inverse square of diameter

Continuity says the volumetric flow through a closed pipe is the same everywhere, so where the pipe narrows the fluid must speed up. Because area depends on the square of the diameter, halving the bore quadruples the velocity — and since dynamic pressure goes as velocity squared, it rises by a factor of sixteen.

That fourth-power sensitivity is why pipe sizing matters so much and why a partially closed valve or a scaled-up bore changes a system's behaviour far more than the dimensions suggest.

For water in pipes the practical velocity range is roughly 1 to 3 m/s. Slower than about 0.6 m/s and solids can settle out; faster than about 3 m/s and the pipe becomes noisy, erosion accelerates at bends, and friction loss — which grows with the square of velocity — starts to dominate the pump's duty.