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IPC 709
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 IPC 709 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
Fixture units are the currency of plumbing sizing. This app totals the water supply fixture units (WSFU) and drainage fixture units (DFU) for a building from the IPC tables, then converts the supply load to a probable demand in GPM — the starting point for pipe sizing.
How it works
- Add each fixture; the app assigns its WSFU and DFU from the IPC fixture tables.
- It separates cold, hot, and total supply loads for accurate branch sizing.
- It converts total WSFU to peak GPM using Hunter's curve.
Worked example
A typical full bathroom (water closet, lavatory, shower) is roughly 5–7 WSFU on the supply side and about 5–6 DFU on the drainage side, depending on flush-tank versus flush-valve fixtures.
Related calculators
Feed the totals into the water pipe sizing and drainage pipe sizing calculators.
Fixture unit FAQ
What is the difference between WSFU and DFU?
Water supply fixture units measure the demand a fixture puts on the supply piping; drainage fixture units measure the load it puts on the drain system. Each fixture has both values in the IPC.
How do fixture units become GPM?
Hunter's curve converts total water supply fixture units into a probable peak demand in gallons per minute, accounting for the fact that not all fixtures run at once.
Does flush type change the value?
Yes. Flush-valve water closets carry more supply fixture units than flush-tank models, so the app distinguishes them.
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 Fixture Unit Calculator on your phone
Free with rewarded ads · $2.99 lifetime Pro · iOS & Android. Works 100% offline on the job site.