Plumbing Material Takeoff Calculator

Bidding a plumbing rough-in starts with a quick, defensible takeoff: how much pipe, how many fittings, and how big the trunk needs to be. This calculator turns a fixture count and an average run distance into a bid-level material list, so you can price labor and material before measuring every line on the drawing.

How it works

Each fixture contributes supply runs and a drain branch. Fixtures that need both hot and cold add two supply lines; cold-only fixtures such as toilets and hose bibbs add one. Every fixture adds one branch drain. The footage is the run count times the average riser-to-fixture distance, scaled by the waste factor:

supply_ft = (hot+cold lines) x avg_distance x (1 + waste%)
drain_ft  = (fixtures)       x avg_distance x (1 + waste%)

Fittings come from typical branch ratios — roughly two elbows and one trunk tee per supply line, and one sanitary tee plus one and a half elbows per fixture drain. Each fixture also carries a water-supply fixture-unit weighting; summing them gives the total WSFU that drives the trunk-size note.

Tips and example

A small house with two toilets, two lavatories, one tub/shower, a kitchen sink, a dishwasher, a clothes washer, and two hose bibbs at an 18 ft average run and 10 percent waste totals around 22 fixture units and produces roughly a couple hundred feet of supply plus the drain branches, with the trunk note recommending a 1-inch main.

Treat the output as a starting estimate. Tighten it with a measured takeoff for the final purchase order, and always confirm the trunk and branch sizes against the WSFU demand and the plumbing code your jurisdiction enforces.

Fixture unit weights: what drives the trunk size

WSFU weights come from Hunter’s probability model, which assumes fixtures are not all running simultaneously. Common fixture weights (typical values — confirm with your local plumbing code):

Flush-valve toilets carry higher WSFU because they draw water rapidly in a brief burst. In multi-toilet commercial buildings this is often the dominant load on the system and drives a much larger trunk than the fixture count alone would suggest.

Choosing pipe sizes from WSFU totals

Once you have a total WSFU, you can select a trunk size from the Hunter’s Curve tables in IAPMO’s Uniform Plumbing Code or the IPC. As a rough guide:

• Up to about 6 WSFU — 3/4 in supply trunk is often adequate for a single bath or small kitchenette.
• 7–25 WSFU — a 1 in trunk handles most small residential loads.
• 26–100 WSFU — a 1.25 or 1.5 in trunk serves medium residential to small commercial.
• Above 100 WSFU — 2 in and above, confirm with the Hunter’s Curve demand chart.

These are general guidance only; always verify against your specific code edition and the water meter sizing calculation.

Waste factor guidance by project type

The waste factor covers off-cuts, miscuts, fitting tails, and minor rework. Choosing it well keeps your bid accurate:

Remodel waste runs higher because you are working around existing structure, existing pipes may not be where the drawing says, and access is slower. Tight crawlspaces add more off-cuts at irregular angles.

What this takeoff does not cover

The tool produces bid-level footage and fitting counts; it does not account for:

• Vertical riser footage inside walls from the slab to a second or third floor — add these as a separate run for multi-storey jobs.
• Water heater connections, tempering valves, expansion tanks — discrete items best counted from the plans.
• DWV vent pipe — the tool estimates branch drains but not the full vent-to-roof stack footage.
• Meter and service entrance — sized separately by the water utility or engineer.

Use the output as a quick basis for material budgeting, then tighten against the plans for the purchase order.