Pipe size chart

Three sizing systems

Pipe and tube in the US are named three different ways, and the same number means a different diameter in each:

• Nominal pipe size (NPS): steel, stainless and PVC pipe. Each NPS has one fixed outside diameter that does not change with wall thickness. ASME notes that for NPS 12 and smaller the OD is numerically larger than the size: 1/2-inch pipe is 0.840 in OD and 2-inch pipe is 2.375 in. From 14 in up, the NPS equals the OD.
• Copper water tube (Types K, L, M): named by a standard size, and the actual OD is always 1/8 in larger, according to the Copper Development Association. 3/4-inch Type L is 0.875 in OD.
• ACR tube: copper for air conditioning and refrigeration field service, which the CDA says is designated by its actual OD. 7/8-inch ACR is 0.875 in OD, the same tube size as 3/4-inch Type L water tube.

Steel and PVC pipe

Charlotte Pipe and Westlake both list PVC Schedule 40 pipe as iron pipe size (IPS) to ASTM D1785, and Westlake lists its Schedule 80 the same way. The outside diameters match steel pipe: 2-inch PVC and 2-inch steel are both 2.375 in OD. The Schedule 40 walls match steel through 12 in (0.154 in at 2 in). Westlake lists PVC walls as minimums. At 10 and 12 in, Schedule 80 PVC lists 0.593 and 0.687 in where steel lists 0.594 and 0.688 in.

Check the limits before using PVC. ASTM D1785 covers PVC pipe for pressurized liquids only. Charlotte Pipe limits its Schedule 40 PVC pressure pipe to operating temperatures of 140°F or less and warns never to test with, or carry, compressed air or gas in PVC pipe or fittings. For every steel schedule from 5S to XXS, see the pipe schedule chart.

Copper water tube: Types K, L and M

All three types share an OD for each size and differ only in wall, so the ID changes. The CDA notes that Type K has thicker walls than Type L, and Type L thicker than Type M, at any given diameter. For 3/4-inch tube (0.875 in OD):

The chart covers 1/4 to 4 in from the CDA Copper Tube Handbook. The handbook lists Type M from 3/8 in and skips 5/8 in; Mueller Streamline also sells Type M in 1/4 and 5/8 in, which the chart leaves out because only one of our sources lists them.

ACR tube and line sets

ACR tube comes in two tempers with different walls. ASTM B280 and the CDA handbook describe annealed (soft) tube supplied in coils and drawn (hard) tube supplied in straight lengths. Drawn ACR has the same dimensions as Type L water tube of the same OD, so 3/4-inch drawn ACR is 5/8-inch Type L; Mueller lists the two together as Type L / ACR. Some sizes differ by temper:

• 3/8 in OD: annealed 0.032 in wall, 0.311 in ID; drawn 0.030 in wall, 0.315 in ID.
• 1/2 in OD: annealed 0.032 in wall, 0.436 in ID; drawn 0.035 in wall, 0.430 in ID.
• 3/4 in OD: annealed 0.035 in wall, 0.680 in ID; drawn 0.042 in wall, 0.666 in ID.

From 7/8 in up the two tempers have the same wall. The line-set charge calculator uses the annealed (coil) IDs. Internal volume per foot = 0.7854 x ID² x 12 cubic inches: a 3/8-inch annealed liquid line holds 0.912 cubic inches per foot.

Identifying pipe by measuring it

Measure the outside diameter with a caliper and match it, then check the wall to tell the type or schedule:

• 0.625 in: 1/2-inch copper water tube or 5/8-inch ACR.
• 0.840 in: 1/2-inch steel or PVC pipe.
• 0.875 in: 3/4-inch copper water tube or 7/8-inch ACR.
• 1.050 in: 3/4-inch steel or PVC pipe.
• 1.125 in: 1-inch copper water tube or 1-1/8-inch ACR.
• 1.315 in: 1-inch steel or PVC pipe.

IDs in the chart are calculated as OD minus twice the nominal wall, or the minimum wall for PVC, the way Westlake calculates its PVC IDs. Real pipe and tube are made to tolerances: ASTM A53 steel pipe, as Wheatland lists it, may run up to 12.5% under the nominal wall at any point, so a measured ID can differ.