Steam Pipe Sizing Calculator
The inside diameter, the nearest standard pipe size and the actual velocity for a steam flow at a target velocity.
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How this calculator works
Steam pipes are commonly sized by velocity. From the steam flow and the specific volume at the pressure you get the volume flow. Divide by the target velocity for the area, then find the diameter. The calculator then picks the smallest standard Schedule 40 pipe with enough bore and gives the actual velocity in it.
Saturated steam lines are commonly designed for about 15 to 40 m/s, depending on the pressure, the allowed pressure drop and noise. Check the pressure drop over the whole length as well as the velocity.
Formulas used
- Q = \dot m\,v_g
- A = Q / v
- D = \sqrt{4A/\pi}
Worked example
With the default numbers in the calculator above:
- Steam volume flow: 0.1192 m³/s
- Area for the target velocity: 47.69 cm²
- Inside diameter needed: 77.92 mm
- Nearest standard pipe (Schedule 40) with enough bore: DN100, bore 102.3 mm
- Actual velocity in that pipe: 14.52 m/s
Change the numbers in the calculator to see the full working, every step, for your own case.
Common questions
What velocity is typical for steam?
About 15 to 40 m/s for saturated steam. Lower for short lines and low noise, higher for long runs with a large pressure available.
Does it check the pressure drop?
No. It sizes by velocity. A long line needs a pressure drop check.
Which pipe sizes are used?
ASME B36.10 Schedule 40 sizes. Confirm with your supplier.
Related calculators
Further reading: Cengel and Boles, Thermodynamics: An Engineering Approach; Moran and Shapiro, Fundamentals of Engineering Thermodynamics. Steam system suppliers' sizing guides.
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