Pipe Size Calculator
The Pipe Size Calculator determines the minimum required pipe internal diameter for a given flow rate and design velocity. Includes nominal pipe size (NPS/DN) recommendation.
Educational estimate. Calculator results are for planning and information only, not financial, tax, medical, legal, or engineering advice. Verify important decisions with official sources or a qualified professional.
Pipe Size Calculator
Required Pipe Diameter from Flow Rate
📐 Formula & Method
Continuity Equation
Q is volumetric flow rate in m3/s, A is pipe cross-sectional area in m2, and v is design velocity in m/s.
Pipe Diameter
Flow is entered in L/min and converted to m3/s by dividing by 60,000. Diameter is reported in millimetres.
📋 How to Use
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1
Enter the required flow rate in L/min.
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2
Enter a design velocity in m/s.
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3
The calculator converts flow to m3/s, computes internal diameter, and rounds up to the next listed nominal DN size.
🧮 Worked Examples
Validation case
200 L/min at 1.5 m/s.
Pipe Size Calculator — Engineering Reference
This calculator uses the continuity equation to estimate minimum internal pipe diameter from a target velocity.
It is preliminary sizing only. Final pipe selection must also consider pressure drop, pipe schedule, roughness, fittings, fluid viscosity, erosion limits, and code requirements.
🔬 Methodology & Accuracy
Formula: Converts L/min to m3/s, divides by selected velocity to get pipe area, calculates internal diameter from circular area, and recommends the next larger nominal DN size from a simple lookup list.
Data sources: Continuity equation from standard fluid mechanics; common preliminary water velocity guidance.
Last reviewed: June 2026 · General formula used: Continuity Equation · Accuracy: Results are precise to two decimal places using IEEE-754 double-precision arithmetic. Intended for educational and planning use only.
For informational purposes only. Results are estimates based on the inputs and formulas provided. For financial, tax, medical, or legal decisions, consult a qualified professional. Rates and regulations change — always verify current figures with official sources.