Flow Rate Calculator

Convert between volumetric flow rate, pipe area and fluid velocity.

About Flow Rate Calculator

Flow rate is area times velocity. Because area scales with the square of diameter, a pipe twice as wide carries four times the flow at the same velocity. Doubling pipe diameter quadruples capacity at constant velocity, which is why small increases in pipe size relieve bottlenecks so effectively.

Formula

Flow Rate

Q = A v, with A = π (d ÷ 2)²

Q: Volumetric flow rate
A: Cross-sectional area of the pipe

Worked example

With the default values below, Flow Rate Calculator returns Volumetric Flow Rate of 15.708. Change any input above and every figure here is recalculated in your browser.

Inputs used

Pipe internal diameterminimum 0.1 mm: 100 mm
Fluid velocityminimum 0 m/s: 2 m/s
Fluid densityminimum 0.01 kg/m3: 1,000 kg/m3

Results

Volumetric Flow Rate: 15.708 L/s
Volumetric Flow Rate: 56.549 m3/h
Mass Flow Rate: 15.708 kg/s
Cross-Sectional Area: 0.007854 m2
Volumetric Flow Rate: 942.48 L/min

Step by step

1Values used
2Flow Rate
3Volumetric Flow Rate= 15.708 L/s
4Volumetric Flow Rate= 56.549 m3/h
5Mass Flow Rate= 15.708 kg/s
6Cross-Sectional Area= 0.007854 m2
7Volumetric Flow Rate= 942.48 L/min

Assumptions and limits

The result is derived only from the 3 inputs listed above. Anything not among them is not part of the calculation.
In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
Figures are rounded for display to 6 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

Frequently Asked Questions

How is Flow Rate calculated?

Q = A v, with A = π (d ÷ 2)² Flow rate is area times velocity. Because area scales with the square of diameter, a pipe twice as wide carries four times the flow at the same velocity.

Why does Flow Rate matter?

Doubling pipe diameter quadruples capacity at constant velocity, which is why small increases in pipe size relieve bottlenecks so effectively.

What values do I need to enter?

This calculator takes 3 inputs: Pipe internal diameter, Fluid velocity, Fluid density. The pre-filled defaults are a realistic starting point — replace them with figures from your own environment for a result you can act on.