The calculation, without hidden assumptions
Pipe capacity is controlled by the actual inside diameter, not the nominal name printed on a pipe. Because area scales with diameter squared, even a modest bore difference can materially change the stored volume. MAXScanner lets you enter the bore directly or derive it from outside diameter and wall thickness, then applies length, identical-run quantity and an optional fittings-length allowance. For a horizontal pipe that is not full, the same circular-segment geometry used for a horizontal tank converts liquid depth into current volume. Density and flow remain optional user inputs for mass, fill time, drain time and velocity.
How to use this calculator
Enter actual inside diameter when you know it, or choose outside-diameter mode and enter OD plus wall thickness so the bore is derived explicitly.
Enter straight-run length, number of identical runs and any project-specific equivalent-length allowance; use liquid depth as a percentage of inside diameter when the horizontal pipe is partially filled.
Optionally enter fluid density and inlet flow in L/min to see current liquid mass, remaining volume, fill/drain time and flow velocity; use hydraulic calculators for pressure-loss or pipe-sizing work.
Where people use it
- •Water-system fill, drain and flushing volume checks
- •Dosing and chemical quantity planning from actual pipe bore
- •Estimating partial liquid volume in horizontal gravity lines
- •Comparing repeated pipe runs, fluid weight and simple fill time
Example: 100 mm ID pipe, 6 m long
A full 100 mm bore has about 7.854 litres per metre, so a 6 m run holds about 47.12 litres before any additional equivalent length or repeated-run quantity is applied.
What the result does not assume
- •Nominal pipe size is not the inside diameter. Use a measured bore or verified manufacturer/standard dimensions for the actual material and schedule.
- •Equivalent-length allowance is only a volume convenience. It is not a friction-loss equivalent-length calculation and does not size fittings, pumps or pipes.
- •Flow velocity and time use the entered steady volumetric flow. They do not model pressure, compressibility, pump curves, friction losses or changing flow.
Frequently asked questions
Should I use pipe inside or outside diameter?+
Use inside diameter for fluid capacity. If you only have outside diameter, choose OD + wall thickness and MAXScanner subtracts twice the wall thickness to derive the bore.
Can it calculate a half-full horizontal pipe?+
Yes. Enter liquid depth as a percentage of the inside diameter. The calculator uses circular-segment area rather than assuming volume percentage equals depth percentage.
Can I calculate several identical pipes?+
Yes. Enter the number of identical runs and the current/full volume is multiplied by that quantity.
Does this calculator size a pipe from flow?+
No. It reports capacity and, when flow is entered, simple time and velocity. Pipe sizing requires hydraulic criteria and applicable design requirements.
Semantic next steps
Continue the calculation
These links move to a different input, formula or project stage rather than a keyword variation of this page.
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Keep the result connected to the real job
MAXScanner keeps the formula and assumptions beside the result so you can verify the number before using it in a drawing, estimate, specification, worksheet or document. Where a supplier, manufacturer, drawing or applicable standard owns a requirement, that source remains authoritative.