Do toilets affect drain size here?
Yes—any toilet count forces at least a 3" drain recommendation.
Count toilets, sinks, showers, tubs, dishwashers, washers, and hose bibs. The tool multiplies each count by fixed WSFU and DFU values, sums the totals, and recommends supply and drain pipe sizes from simplified tables.
If any toilets are present, drain size is raised to at least 3". Results are planning estimates—verify with local IPC/UPC and the authority having jurisdiction (AHJ).
Concise answers for common searches — definitions, steps, and comparisons.
Yes—any toilet count forces at least a 3" drain recommendation.
Total WSFU from your fixture counts.
Total WSFU and DFU are summed from fixture counts, then mapped to supply and drain diameter bands. Toilets force a minimum 3" drain recommendation.
Formula
WSFU/DFU per fixture: toilet 3/3, sink 1.5/1, shower 2/2, tub 4/2, dishwasher 1.5/1, washer 2.5/2, hose bib 2.5/0. Supply size from WSFU bands (e.g. ≤8→1/2", ≤12→3/4", ≤30→1", …). Drain size from DFU bands, with toilets requiring at least 3".Fill toilets, sinks, showers, tubs, dishwasher, washer, and hose bibs for the branch or dwelling you are planning.
The results panel shows supply size from WSFU and drain size from DFU.
If any toilets are counted, drain size is at least 3" in this calculator’s recommendation.
Treat sizes as a starting point and verify with IPC/UPC tables and a licensed plumber.
Input
2 toilet · 3 sink · 1 shower · 1 tub · 1 DW · 1 washer · 1 hoseOutput
Supply 1" · Drain 3"Totals ≈ 23 WSFU and 16 DFU; supply band ≤30 → 1"; drain with toilets → 3".
Input
1 toilet · 1 sink · 1 showerOutput
Smaller WSFU/DFU totals than a whole-house countWSFU = 3+1.5+2 = 6.5; DFU = 3+1+2 = 6 before mapping to size bands.
Common real-world scenarios where this tool saves time.
Default mix (2 toilets, 3 sinks, 1 shower, 1 tub, appliances, 1 hose bib) → about 23 WSFU (1" supply) and 16 DFU (3" drain).
Lower fixture counts to estimate a bathroom group supply/drain size before confirming code tables.
Hose bibs increase supply WSFU only in this model—useful when outdoor faucets share the supply.
Step-by-step chains that connect related tools for common tasks.
Estimate diameters here, then check drain slope on long runs.
| Fixture | WSFU | DFU |
|---|---|---|
| Toilet | 3 | 3 |
| Sink | 1.5 | 1 |
| Shower | 2 | 2 |
| Tub | 4 | 2 |
| Dishwasher | 1.5 | 1 |
| Washer | 2.5 | 2 |
| Hose bib | 2.5 | 0 |
Whole-house counts oversize a single bathroom branch; branch counts understate a main.
WSFU/DFU values and size charts vary by code edition—confirm locally.
Use local code tables and a licensed plumber for construction documents.
Any toilet count forces at least a 3" drain recommendation in this tool.
This estimates diameter from fixture units. Use the Pipe Volume Calculator for gallons inside a pipe.
Advertisement
WSFU (water supply fixture units) drive supply pipe size. DFU (drainage fixture units) drive drain pipe size. Values here are simplified planning factors.
Fixture counts are multiplied by WSFU factors, summed, then mapped to diameter bands (for example ≤30 WSFU → 1").
DFU totals map to drain diameter bands. If any toilets are included, the recommendation is at least 3".
No. It only maps fixture-unit totals to simplified size charts.
No. It is a simplified estimate. Official sizing must follow the adopted code and AHJ requirements.
Toilet, sink, shower, tub, dishwasher, washer, and hose bib counts (each 0–20).
Pipe sizing inputs remain local — EverydayTools does not collect pipe-sizing calculator entries.
Estimates only — not professional plumbing advice. Verify with a licensed plumber and local code before installation.
Advertisement
Reviewed on 2026-06-28.
Same workflow or intent — pick the next step without leaving the site.
Calculate how much concrete you need for slabs, footings, post holes, columns and steps. Get cubic yards, cubic feet, cubic meters and bag counts with optional waste.
Calculate how much PEX tubing you need in linear feet, add waste, and round up to full coils. Free PEX calculator for plumbing runs and material takeoffs.
Free pipe volume calculator: inside diameter and length → US gallons, liters, cubic feet, water weight, and gallons per foot.
Free drain slope calculator: horizontal run and slope in/ft → total drop and percent grade with IPC minimum check. Runs locally in your browser.
Free water heater calculator: household size → tank gallon size or tankless GPM and BTU/hr. Tank and tankless modes. Runs locally in your browser.
Use our free septic tank calculator to estimate the right tank size from bedrooms, occupants and wastewater flow. Get gallons, daily flow and a clear sizing breakdown.
Frequently opened tools from the same category.
Free adult BMI from height and weight (lb/ft/in or kg/cm). CDC category, healthy weight range, optional waist. Screening only—runs in your browser.
Estimate how many calories you need per day. Mifflin-St Jeor BMR, activity TDEE, and lose/gain starting points. US and metric. Runs in your browser.
Free tip calculator — find tip amount, bill + tip total, and per-person share. Presets for common percentages (10%, 15%, 20%), custom %, and equal split. Runs in your browser. No signup.
What is 20% of 500? Percent increase, decrease, difference, reverse %, markup & margin—runs locally in your browser, no upload. Copy results or share a link.
Cross-category tools others open in the same session.
What is 20% of 500? Percent increase, decrease, difference, reverse %, markup & margin—runs locally in your browser, no upload. Copy results or share a link.
Free JSON formatter — paste minified or messy JSON and instantly get beautified, indented output with syntax highlighting and error detection. Browser-based, no server upload. Runs locally in your browser when supported—no upload required for normal use.
Free word counter — live word, sentence, and paragraph counts plus reading time for essays, blogs, and SEO drafts. Runs locally in your browser.
Free adult BMI from height and weight (lb/ft/in or kg/cm). CDC category, healthy weight range, optional waist. Screening only—runs in your browser.
Guides and walkthroughs that reference this tool.
10 free browser calculators: BMI, tip, discount, overtime, GPA, compound interest. No upload—runs locally. No signup.
2026 roundup of BMI calculators—EverydayTools, CDC, NIH, Healthline, and Calculator.net compared on accuracy, privacy, units, and clinical context.
Browse full tool collections by topic.
Enter how many of each fixture connect to the branch or main you are sizing.