XunLMove cross-border work forward
English
中文EnglishEspañolDeutsch

Pipe Size Calculator

Use velocity to estimate a round pipe bore. Supply the flow and target velocity; the result is a geometric internal diameter, without automatic DN, NPS, schedule or catalogue selection.

Local calculation · inputs stay in your browser

Inputs

Results

    An input link contains the values you entered. Share only information you want to disclose.

    YOUR NEXT STEP

    Keep engineering calculations free and connect your business

    Continue using the free engineering calculations. Create a company account for website monitoring, inquiry handling and team notifications when you need to connect the work that follows.

    Create company accountExplore ProContact us

    New companies receive a 14-day Pro trial, with no card required. Trials exclude the paid monthly credit grant.

    Already have an account? Open your workspace →

    Formula and method

    Q = Av; A = Q/v; D = √(4Q/(πv)). With Q in m³/s and v in m/s, D is in metres, then converted to mm and inches (1 in = 25.4 mm).

    Worked example

    At 10 m³/h and 1.5 m/s, the calculated bore is about 48.558 mm (1.912 in). This is not a nominal-size recommendation.

    Assumptions and limits

    • Use volumetric flow at actual pipe conditions. Standard gas flows such as Nm³/h or SCFM cannot be entered directly.
    • The target velocity is a design input, not a universal limit. Choose it for the fluid, noise, erosion, pressure loss and applicable requirements; this tool does not solve compressible flow.
    • After choosing a commercial pipe, recheck velocity and pressure loss using its actual bore. Wall thickness, pressure rating and mechanical strength are not checked.

    Frequently asked questions

    Why is the result not a nominal size such as DN50?

    A nominal size does not uniquely determine the bore; material and wall thickness change the flow area. Compare the calculated internal diameter with the specific pipe specification.

    What happens if I raise the target velocity?

    For the same flow, a higher target velocity gives a smaller bore. Since D ∝ 1/√v, doubling velocity reduces diameter to about 70.71%.

    References

    Pipe Size Calculator practical guide and common questions

    What does Pipe Size Calculator calculate?

    Use velocity to estimate a round pipe bore. Supply the flow and target velocity; the result is a geometric internal diameter, without automatic DN, NPS, schedule or catalogue selection. Q = Av; A = Q/v; D = √(4Q/(πv)). With Q in m³/s and v in m/s, D is in metres, then converted to mm and inches (1 in = 25.4 mm).

    When is this useful?

    At 10 m³/h and 1.5 m/s, the calculated bore is about 48.558 mm (1.912 in). This is not a nominal-size recommendation.

    How do I enter the inputs?

    Enter the inputs for Pipe Size Calculator: Actual volumetric flow, Flow unit, Target mean velocity. Calculate, check the units and assumptions, then copy or download the results.

    How should I interpret the results?

    Use volumetric flow at actual pipe conditions. Standard gas flows such as Nm³/h or SCFM cannot be entered directly. The target velocity is a design input, not a universal limit. Choose it for the fluid, noise, erosion, pressure loss and applicable requirements; this tool does not solve compressible flow. After choosing a commercial pipe, recheck velocity and pressure loss using its actual bore. Wall thickness, pressure rating and mechanical strength are not checked.

    Where are my inputs processed?

    Pipe Size Calculator runs in this browser. Inputs are not uploaded to a calculation server; copying and CSV download require your action. The existing site analytics and advertising still load.