ABS Pipe Sizes Chart: Dimensions for Every Diameter
Buying a fitting that does not fit is the classic plumbing-store frustration — and it almost always comes down to one confusion: nominal size is not the actual size. A "3-inch" ABS pipe is not 3 inches in any measurable dimension. This chart gives you the real numbers (outside diameter, inside diameter and wall thickness) for every common ABS DWV size so you buy right the first time.
How ABS Pipe Sizing Works
Like most US pipe, ABS follows the iron pipe size (IPS) tradition: the nominal size is a name, not a measurement. The dimensions that matter are:
- Outside diameter (OD) — what fittings, couplings and hangers actually grip. This is the number to match when buying parts.
- Inside diameter (ID) — determines flow capacity. ID = OD minus twice the wall thickness.
- Wall thickness — set by ASTM D2661 minimums for DWV pipe; thicker walls (Schedule 40) exist for pressure or heavy-duty uses.
The good news: ABS and PVC DWV pipe of the same nominal size share the same OD dimensions, which is why one transition coupling can join them.
Complete ABS DWV Dimensions Chart
Dimensions per ASTM D2661 for solid-wall ABS DWV pipe. All measurements in inches.
| Nominal Size | Outside Diameter (OD) | Min. Wall Thickness | Inside Diameter (ID, approx.) |
|---|---|---|---|
| 1-1/4" | 1.660 | 0.140 | 1.380 |
| 1-1/2" | 1.900 | 0.145 | 1.610 |
| 2" | 2.375 | 0.154 | 2.067 |
| 3" | 3.500 | 0.216 | 3.068 |
| 4" | 4.500 | 0.237 | 4.026 |
| 6" | 6.625 | 0.280 | 6.065 |
Note that 1-1/4" pipe has an OD of 1.660" — a full 3/8" larger than its name suggests. This is exactly why "eyeballing it" at the store fails.
How to Measure Your Pipe
No calipers? No problem. Three reliable methods:
- Calipers (best): measure straight across the outside of the pipe. Match to the OD column above.
- Tape around, then divide: wrap a flexible tape around the pipe, note the circumference, and divide by 3.1416 to get the OD. A 3" pipe measures about 11 inches around (3.500 × π ≈ 11.0").
- Read the print line: legitimate ABS pipe has its nominal size printed along its length ("3 IN ABS DWV ASTM D2661"). If the print is legible, you do not need to measure at all — see our pipe identification guide for reading markings.
What Each Size Is Used For
| Nominal Size | Typical residential uses |
|---|---|
| 1-1/4" | Bathroom sink (lavatory) drains, small trap arms |
| 1-1/2" | Kitchen sinks, lavatories, tub/shower trap arms, dishwasher drains |
| 2" | Showers, washing machines, branch drains serving multiple fixtures |
| 3" | Toilet drains, main branch lines, vent stacks |
| 4" | Building drain, building sewer, main stacks in larger homes |
| 6" | Commercial work, large building sewers — rare in single-family homes |
Minimum sizes are set by code based on fixture units — when in doubt, the code minimum wins over "it looks big enough." Undersized drains are a top cause of chronic slow drainage and gurgling.
Schedule 40 vs DWV Wall: What's the Difference?
You will see two wall types on the shelf:
- DWV (drain, waste and vent) — thinner wall, lighter, cheaper. Sized for gravity drainage only. This is what nearly all residential drain pipe is.
- Schedule 40 — thicker, heavier wall rated for pressure applications. Sometimes used for DWV where extra strength is wanted (under slabs, commercial), but it costs more and the thicker wall slightly reduces ID.
- Cellular (foam) core — a DWV variant with a foamed middle layer: lighter and quieter, same OD so it takes standard fittings. Common and code-accepted for DWV.
For gravity drains, standard DWV wall is the right (and cheapest) choice. Do not use DWV pipe or fittings on pressurized supply lines — learn what ABS is actually rated for in our complete ABS pipe guide.