Pipe Schedule Chart — Schedule 40 & 80 Dimensions

How pipe schedules work

For a given nominal size, the outside diameter is fixed — that is what lets fittings fit. The schedule number sets the wall thickness: a higher schedule means a thicker wall, a higher pressure rating and a smaller bore. So Schedule 80 always has a smaller inside diameter than Schedule 40 of the same size, and it holds a little less per foot. The chart below gives both, along with the gallons-per-foot each bore holds.

Schedule 40 & 80 dimensions and capacity

Nominal size is not the diameter

The chart makes the key rule obvious: for sizes up to 12 inch, the nominal number matches neither the outside nor the inside diameter. A "2-inch" pipe is 2.375 in on the outside and 2.067 in on the bore for Schedule 40. From 14 inch upward, the nominal size does equal the outside diameter. Whenever you calculate volume, use the inside diameter from this chart — never the nominal figure.

Does this chart apply to PVC?

Yes. PVC pressure pipe in Schedule 40 and 80 shares these outside and inside diameters, so the bores here are correct for both steel and PVC of the same schedule. CPVC pressure pipe generally follows the same schedule dimensions. Copper, PEX and HDPE are sized by different standards and have their own bores — use the dedicated calculators for those.

Turning the chart into a volume

Two ways to use it. For a quick estimate, take the gallons-per-foot for your size and schedule and multiply by the length. For an exact figure at any length, fill level or unit, select the schedule and size in the calculator above and it loads the chart bore automatically. Either way, the chart is the bridge between a size on a drawing and the water in the pipe.

Source and accuracy

The dimensions follow ASME B36.10 for welded and seamless wrought-steel pipe, which is the standard North American reference and the basis for PVC schedule sizing too. Values are nominal; real pipe carries manufacturing tolerances, and lining, scale or corrosion changes the effective bore in service. For critical work, confirm against the current standard and the manufacturer's data.

Reading and trusting your result

A volume figure is only useful if you know what it assumes — so a quick word on reading your pipe schedule chart result.

How to interpret the result

The headline value is the internal capacity of a round, uniform pipe running full — the fluid the bore can hold along the length you entered. Every other unit on the panel is the same physical quantity re-expressed, so you can quote whichever your paperwork needs without recalculating.

The full-pipe assumption

By default the figure assumes the pipe is completely full and perfectly cylindrical. For gravity drains and vented lines that run part full, set a fill level below 100% and the result scales with it. Bends, valves and fittings add a little capacity the straight-length model does not see — use the fittings allowance to approximate them.

Capacity reference tables & a worked example

Concrete numbers for this page, calculated the same way the tool above does — use them as a quick check or a lookup.

Schedule 40 2" pipe: volume by run length

How much a 2" Schedule 40 bore holds as the run gets longer, in US gal. The per-foot figure is constant, so any length is one multiplication away.

Schedule 40 pipe: volume across sizes

Volume held by a fixed 100 ft run across common Schedule 40 sizes, in US gal. Doubling the diameter roughly quadruples the capacity.

Worked example, step by step

1. Bore = 2.067 in, so radius = 1.0335 in.
2. Area = π × radius² = 3.3556 in².
3. Length = 75 ft = 900 in; volume = 3.3556 × 900 = 3,020.0 in³.
4. Convert to the unit you need: 13.07 US gal for a 75 ft run of Schedule 40 2" pipe.

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