Flow Rate Calculator

What Is Volumetric Flow Rate?

Volumetric flow rate $Q$ is the fluid volume passing through a cross-section each second. For steady pipe flow, it equals cross-sectional area times average velocity.

Flow Rate Formulas

$$\dot{V} = A \cdot v$$

For a circular pipe with internal diameter $d$:

$$\dot{V} = \pi \left(\frac{d}{2}\right)^2 v$$

Mass flow rate from density $\rho$:

$$\dot{m} = \rho \cdot \dot{V}$$

Example: a 3 in pipe at 10 ft/s gives about 0.491 ft³/s of flow. Water at 998 kg/m³ yields roughly 30.6 lb/s mass flow. Related tools: IV Flow Rate Calculator, Pipe Volume Calculator, and Aquarium Volume Calculator.

Frequently Asked Questions

What is the difference between volumetric and mass flow rate?

Volumetric flow is volume per time (m³/s). Mass flow multiplies that volume by fluid density (kg/s).

How do I find velocity from flow rate?

Rearrange to $v = \dot{V} / A$. Divide the known flow rate by the pipe cross-sectional area.

Does pipe diameter affect flow rate at fixed velocity?

Yes. Flow rate scales with the square of diameter because area grows as $\pi d^2 / 4$.

What density should I use for water?

About 998 kg/m³ at 20 °C is a good default. Density changes with temperature and salinity.

Can this calculator handle non-circular ducts?

Yes. Choose rectangular duct or enter a known cross-sectional area directly.

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Flow Rate Calculator

What Is Volumetric Flow Rate?

Flow Rate Formulas

Frequently Asked Questions

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