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ASHRAE
Validated against the standard.
PDF export
Pro-only. Generate professional reports.
$2.99 Pro
Lifetime unlock. No subscriptions.
How it works
Enter your values
Type in your inputs — the app fills code tables and constants for you, so there's nothing to look up.
Get a code-checked result
Instant answer with a clear PASS / FAIL and the exact ASHRAE reference behind every number.
Save & export
Keep a history of calculations and export a clean PDF report to share or attach to a permit (Pro).
What this calculator does
Pipe sizing for HVAC keeps fluid moving at a sensible velocity without excess pressure drop. Undersize the pipe and pumps work harder and the system gets noisy; oversize it and you waste money. This app sizes hydronic and refrigerant piping from flow and a target velocity, following ASHRAE practice.
How it works
- Enter the flow — GPM for hydronic water systems, or capacity for refrigerant lines.
- The app sizes the pipe to keep velocity in range — typically about 2–4 ft/s for closed-loop hydronic to limit noise and erosion.
- It reports the resulting friction loss per 100 ft so you can check pump head.
Worked example
About 8 GPM in a copper hydronic loop sizes to roughly 3/4-inch pipe to stay near 4 ft/s; pushing the same flow through 1/2-inch pipe drives velocity and noise too high.
Related calculators
For refrigerant work, pair it with the superheat and subcooling calculator and the refrigerant charge calculator.
Pipe sizing FAQ
What velocity should hydronic pipe target?
Closed-loop hydronic systems are commonly sized for about 2 to 4 ft/s to balance pump energy against noise and erosion. The app flags sizes that fall outside the range.
Does it report friction loss?
Yes. It returns the friction loss per 100 ft for the chosen size so you can add it up across the loop and size the circulator pump.
Hydronic and refrigerant?
Yes, it handles water-based hydronic piping and refrigerant line sizing by capacity, since each has its own velocity and pressure-drop targets.
Does it work offline?
Yes, it runs 100% offline with no account. Free with rewarded ads; a one-time $2.99 Pro unlock adds PDF export and saved history.
Get Pipe Sizing on your phone
Free with rewarded ads · $2.99 lifetime Pro · iOS & Android. Works 100% offline on the job site.