Drain size calculator
The smallest drain pipe for your total drainage fixture units, from your region's table. An estimate.
Drain size
Done.
–Pipes
Need (exact)
Details
How we got it
pipe = smallest drain with max DFU ≥ total DFU
Estimate — confirm with local code and a licensed plumber.
Estimate only — bag yields vary by brand. Check your local building code.
How to use it
- Type your measurements. Feet-inch (12' 6 1/2"), decimal feet and metric all work; a bare number means feet or metres.
- Need is the exact amount. Buy rounds up to whole bags, sheets or pieces, with the waste % included.
- "How we got it" shows the formula, so you can check every number.
- A "Check this" note means a value looks unusual. Have a look before you buy.
Save it to a project
Keep this calculation with the job and add it to your shopping list. Free in your browser; price it and quote it with Pro.