Flow Rate Calculator

Volumetric Flow Rate

Volumetric flow rate (Q) measures the volume of fluid passing through a cross-section per unit time. It is fundamental in fluid mechanics, hydraulics, and HVAC engineering.

• Q = Volume flow rate (m³/s)
• A = Cross-sectional area (m²)
• v = Average flow velocity (m/s)

How to use this calculator

1. Enter the cross-sectional area of the pipe or channel as \(A\).
2. Enter the fluid velocity as \(v\).
3. Use the calculator to compute flow rate \(Q\) from \(Q = A \times v\).
4. Check the result units, since area and velocity units must match the flow rate units.

The formula explained

The formula \(Q = A \times v\) computes volumetric flow rate, which is the volume of fluid moving past a point per unit time. If area is in square meters and velocity is in meters per second, then flow rate is in cubic meters per second.

• Q = flow rate, the volume of fluid per unit time
• A = cross-sectional area of the flow
• v = fluid velocity

Step by step method

1. Write down the area \(A\) and the velocity \(v\).
2. Multiply them using \(Q = A \times v\).
3. Attach the correct units to the answer, such as \(\text{m}^3/\text{s}\) if \(A\) is in \(\text{m}^2\) and \(v\) is in \(\text{m}/\text{s}\).

Worked example

Problem. A pipe has a cross-sectional area of \(0.20\,\text{m}^2\) and water moves through it at \(3.5\,\text{m}/\text{s}\). Find the flow rate.

1. Use the formula \(Q = A \times v\).
2. Substitute the values, \(Q = 0.20 \times 3.5\).
3. Calculate \(Q = 0.70\,\text{m}^3/\text{s}\).

Tips and common mistakes

• Make sure the area is the area perpendicular to the flow, not the surface area of the whole pipe.
• If your units are not consistent, convert them first, because mixed units can give a wrong flow rate.

Frequently asked questions