Volumetric Flow Rate

This formula says that the volume of fluid moving past a point each second depends on two things: how wide the passage is and how fast the fluid is moving. If you imagine a tube or channel, the fluid in a short time interval occupies a length equal to speed × time, so the volume moved is area × length = A × v × t; dividing by time gives Q = Av. This works when the flow is steady and the speed is roughly uniform across the cross-section.

Use this when you want to find how much liquid or gas passes through a pipe, hose, river section, or nozzle per second. It is common in hydraulics, plumbing, ventilation, and basic physics problems involving flow in a uniform channel.

• Using the diameter instead of the cross-sectional area
• Forgetting to convert units so area is in m^2 and speed is in m/s
• Confusing volumetric flow rate with mass flow rate