Pipe Sizing Calculator. Audit source-labelled flow, velocity, circular area and theoretical inside-diameter arithmetic against one already documented candidate ID—without selecting nominal pipe, material or compliance.
A quick decision brief for this specific tool
One de-identified reviewed hydraulic segment; named flow, velocity and candidate inside-diameter sources; one paired GPM/ft-per-second/inch or litre-per-second/metre-per-second/millimetre unit system; and positive documented flow, velocity and candidate inside diameter
Source-preserving converted flow, theoretical circular area and inside diameter, candidate area, plus signed candidate-minus-theoretical diameter and area differences
Convert the entered flow within its paired unit system, apply Q = A x V and circular geometry, then compare an already documented actual candidate inside diameter; do not derive WSFU demand, choose velocity, round to nominal pipe, select material or declare minimum/compliance
Choose your path
Reproduce source-labelled flow, velocity, circular area and theoretical inside-diameter arithmetic, then compare one already documented candidate inside diameter without selecting nominal pipe, material or compliance.
Check continuity arithmetic without a generic nominal-size list replacing the material and pressure-loss design.
Name the flow, velocity and candidate-ID sources; choose one paired unit system; inspect theoretical area/diameter and signed candidate differences.
Can trace every value while demand, velocity, material and final size selection remain in the responsible design.
Distinguish actual inside diameter from nominal/trade size and expose hidden GPM conversion.
Inspect the source cards, unit basis, converted flow, Q divided by V and candidate-minus-theoretical arithmetic.
No standard-size rounding, minimum-pipe recommendation or compliance verdict is generated.
Learn why one velocity equation cannot decide PEX, copper or another complete distribution system.
Run separate US and metric education records using actual candidate inside diameters from named sources.
Can reproduce the geometry and list pressure, friction, length, fittings, temperature, surge and approval checks the tool omits.
Outputs and checklists are planning aids. Review the linked current authorities and the records, terms, instructions, and requirements that apply to your exact situation before a consequential decision.
Tools you might need next
Reproduce circular area and volumetric flow from a source-labelled actual inside diameter and documented average velocity, then compare an independent flow record without selecting demand, capacity or compliance.
Audit a source-labelled pressure-component ledger against an independent endpoint record—without inventing friction/elevation losses, clamping pressure or selecting pipe, pump or regulator.
Audit source-labelled drain-segment fall, slope and percent grade against an already documented comparison slope—without selecting a minimum, pipe, drainage method or compliance.
Flow demand or measurement, the selected review velocity and the candidate's actual inside diameter can come from different responsible records. The tool keeps them named instead of deriving WSFU demand, choosing a velocity or treating nominal size as actual ID.
Record = flow source + velocity source + candidate-ID sourceUS entries convert GPM to cubic feet per second before division by ft/s; metric entries convert litres per second to cubic metres per second before division by m/s. The result is theoretical internal flow area and circular inside diameter, not a nominal product size.
A = Q ÷ V; theoretical ID = √(4A ÷ π)Positive, zero and negative differences are source-record comparisons only. They do not establish an undersized, minimum, acceptable or compliant pipe because pressure, friction, material, temperature, length, fittings, transients and installation are outside this equation.
ID difference = entered candidate ID − theoretical IDUpdated: August 2026
A designer copies established flow and velocity plus an actual candidate inside diameter from the submitted calculation/product record. The tool exposes continuity arithmetic without selecting the branch size.
A reviewer uses the exact inside diameter for one material and wall class, not its nominal label. Pressure-drop tables, temperature and installation instructions remain authoritative outside the comparison.
An apprentice enters litres per second, metres per second and millimetres in one paired record, then explains why a signed diameter difference is not a pipe recommendation.
Reproduce one reviewed hydraulic segment without turning one equation into a pipe-selection verdict. Name the responsible flow, velocity and candidate inside-diameter records; use one complete US or metric unit system; and inspect the theoretical circular area/diameter plus signed candidate differences. Demand, allowable velocity, material, pressure loss and approval remain in the complete design.