Q = VA Flow Rate Calculator

Basic flow equation: Q = V × A. Flow rate equals average velocity multiplied by the area perpendicular to flow.

Velocity: V = Q ÷ A. Area: A = Q ÷ V. Circular diameter: D = √(4Q ÷ πV).

Transferred volume: Volume = Q × time. Mass flow: ṁ = ρQ. Continuity: A₁V₁ = A₂V₂.

1. Select the quantity you want to calculate.
2. Choose a cross-sectional shape or enter a custom area.
3. Enter the known values with their matching units.
4. Use a correction coefficient only when required.
5. Press Calculate and review the formula, conversions, and steps.
6. Copy, print, export CSV, or download the result as a PDF.

Volumetric flow rate measures fluid volume passing a section each second. The equation connects flow rate, average speed, and effective area. It applies to liquids, gases, pipes, ducts, and channels.

Velocity must represent the average across the entire cross-section. Local centerline velocity can be higher than the average value. Using the wrong velocity creates an overstated flow result.

Area must be perpendicular to the direction of movement. Circular pipe area uses diameter or radius measurements. Irregular sections need a measured or carefully estimated effective area.

Unit consistency is essential before multiplication or division. This calculator converts entries into SI base units internally. It then converts final values into the chosen display units.

Multiple identical pipes can share or combine a total flow. The pipe count setting multiplies per-pipe capacity for total flow. Reverse calculations divide total flow across the selected pipe count.

The correction coefficient adjusts ideal area and velocity calculations. A coefficient below one can represent losses or reduced effective area. It should not replace a detailed pressure-loss analysis.

The continuity equation compares two sections in steady incompressible flow. A smaller area normally produces a greater average velocity. Both sections carry the same ideal volumetric flow rate.

Mass flow requires density in addition to volumetric flow. Density may change with temperature, pressure, and fluid composition. Use a density that matches actual operating conditions.

Pipe length, roughness, fittings, pressure, and viscosity affect attainable flow. Those factors are not solved by Q equals VA alone. They require hydraulic resistance or pressure-drop calculations.

Calculated diameter represents the ideal internal flow diameter. Real pipe selections should use available nominal sizes and internal diameters. Engineering safety margins may also be necessary.

Use the result table to compare nearby velocity conditions. It helps assess how flow changes at constant area. Always confirm limits from applicable codes and equipment documentation.