Offline
No internet, no account required.
IPC 704
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 704 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
Drain lines need just the right fall: too little and solids settle, too much and water outruns the solids. This app gives the required slope and the drop over a run per IPC 704, and converts between inches per foot, percent, and total fall.
The IPC slope rules
- Pipe 2-1/2 inch and smaller — minimum 1/4 inch per foot.
- Pipe 3 inch to 6 inch — minimum 1/8 inch per foot.
- Pipe 8 inch and larger — minimum 1/16 inch per foot.
- The goal is a flow velocity of at least about 2 ft/s to keep solids in suspension.
Worked example
A 40-foot run of 3-inch drain at the 1/8 inch per foot minimum drops 40 × 0.125 = 5 inches total. The app shows the invert elevations at each end so you can set the pipe.
Related calculators
Size the pipe first with the drainage pipe sizing calculator, then lay it out with the pipe offset calculator.
Drainage slope FAQ
What is the minimum slope for a drain?
Under IPC 704, pipe 2-1/2 inch and smaller needs at least 1/4 inch per foot, 3 to 6 inch needs 1/8 inch per foot, and 8 inch and larger needs 1/16 inch per foot.
Can a drain be too steep?
Very steep drains can let water outrun solids, though the bigger risk in practice is too little slope. The app flags slopes outside the practical range.
Does it convert units?
Yes — between inches per foot, percent grade, and total fall over the run, with invert elevations at each end.
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.
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Free with rewarded ads · $2.99 lifetime Pro · iOS & Android. Works 100% offline on the job site.