33 ft
Plumbing Calculator
Enter fixture pipe runs and counts to get pipe footage with fittings and a DFU-based minimum drain diameter, checked against verified IPC reference rows.
Material ListPipe footage with fittings
Plumbing estimating on this page covers pipe run footage with an editable fitting allowance, and drain sizing by total fixture units (DFU) against IPC reference tables. It is the same Plumbing calculator available on its own page, just presented with the informational context below.
Pipe footage and fixture units (DFU), explained
Measure each fixture’s drain run along the routed path from the fixture to where it joins the branch or building drain, not a straight-line distance. Enter each fixture type separately with its own run length and count, since fixture units and fitting needs differ by fixture.
A Drainage Fixture Unit (DFU) is a standardized load value assigned to each fixture type by the plumbing code, used to size drain and vent piping. A water closet, for example, carries more DFU load than a lavatory. Total DFU load, plus the pipe context (building drain vs. horizontal branch), determines the minimum pipe diameter this calculator checks against.
Fixture runs and pipe sizing
Enter each fixture's run length and count, then pick a pipe context and a diameter to check. Results update as you type, with no Calculate button.
Plumbing
Pipe footage with fittings, plus DFU-based drain diameter sizing.
This run requires 33 ft of pipe sized for 4 DFU.
You'll need
Plumbing result
Warnings
- INFO General reference only. Verify local requirements and adopted code before installation.
- INFO A drain serving a water closet is held to a 3 inch minimum.
Detail values
- Base pipe footage
- 30 ft
- Total DFU
- 4
- Minimum pipe diameter
- 3 in
- Selected pipe check
- Pass
Assumptions
- Fitting allowance: 10% (editable)
- IPC data: IPC 2021 Tables 709.1 and 710.1
Formula details
- Pipe footage: sum(run length x fixture count) x (1 + fitting allowance %)
- Total DFU: sum(fixture DFU x count)
What DFU sizing here does and doesn't cover
DFU load values and drain-capacity rows in this calculator are sourced from IPC 2021 Table 709.1 (fixture unit values) and Tables 710.1(1) and 710.1(2) (drain capacity by pipe diameter). Only the fixture types, pipe contexts, and capacity rows documented in those tables are supported — this calculator does not extrapolate to fixtures or local amendments outside that verified dataset.
When a water closet is part of the run, a 3 inch minimum drain diameter is enforced regardless of the DFU-calculated minimum, matching the code’s water closet minimum requirement. Always verify the locally adopted code before installation, since jurisdictions frequently amend IPC base tables.
FAQ
Why is there only one calculator on this page?
Plumbing's pipe footage and DFU sizing don't have a natural second calculator to chain them to in this release, unlike Roofing's rafters-to-shingles-to-sheathing flow. This page still gives Plumbing the same informational, SEO-focused treatment as the multi-calculator trades.
Are local amendments included in the DFU sizing?
No. Verify the locally adopted code, since jurisdictions frequently amend IPC base tables.
Why are only some fixtures supported for DFU sizing?
Only fixtures with verified IPC Table 709.1 reference values are included. Unsupported fixtures are not guessed.
What is the minimum 3 inch rule for a water closet?
When a water closet is served, the calculator enforces a minimum 3 inch drain diameter regardless of the calculated DFU-based minimum.
Disclaimer
General reference only. Verify local requirements before installation.