Pipe Sizing Calculator

About the Pipe Sizing Calculator

Calculates the internal pipe diameter needed to carry a volumetric flow at a chosen velocity.

How to use this calculator

1. Enter the flow rate, usually in units like \(m^3/s\) or a matching unit for your setup.
2. Enter the target velocity, usually in \(m/s\).
3. Use the calculator to find the pipe diameter that fits that flow and speed.
4. Check the result against your design limits, because real systems may need a standard pipe size next.

The formula explained

The formula calculates the pipe diameter needed for a given volumetric flow rate and flow velocity. It comes from rearranging the area relation \(Q = Av\), then using the circle area formula \(A = \\frac{\\pi d^2}{4}\).

• d = pipe diameter
• Q = volumetric flow rate
• v = flow velocity
• \(\\pi\) = the constant pi, approximately \(3.14159\)

Step by step method

1. Start with \(Q = Av\), because flow rate equals cross-sectional area times velocity.
2. Substitute the circular area formula \(A = \\frac{\\pi d^2}{4}\) into the equation.
3. Rearrange to solve for \(d\), which gives \(d = \\sqrt{\\frac{4Q}{\\pi v}}\).

Worked example

Problem. Find the pipe diameter for a flow rate of \(0.02\\,m^3/s\) at a target velocity of \(2\\,m/s\).

1. Use \(d = \\sqrt{\\frac{4Q}{\\pi v}}\).
2. Substitute the values: \(d = \\sqrt{\\frac{4(0.02)}{\\pi(2)}}\). This gives \(d = \\sqrt{\\frac{0.08}{6.28318}}\).
3. Compute the result: \(d \\approx \\sqrt{0.01273} \\approx 0.113\\,m\).

Tips and common mistakes

• Make sure the units for \(Q\) and \(v\) are compatible, or the diameter will come out wrong.
• If you need a real pipe, compare the calculated diameter with standard pipe sizes and choose the nearest practical option.

Frequently asked questions