Copper pipe is 1/8" wider across the outside than its size, so 1/2" copper is 0.625" (5/8", 15.9 mm) across in Type K, L and M alike. The types differ in wall thickness, which sets the inside diameter.
Copper pipe size chart
Copper pipe size chart
| Size | Outside (OD) | Type K inside | Type L inside | Type M inside |
|---|---|---|---|---|
| 1/4" | 0.375" (9.5 mm) | 0.305" | 0.315" | n/a |
| 3/8" | 0.500" (12.7 mm) | 0.402" | 0.430" | 0.450" |
| 1/2" | 0.625" (15.9 mm) | 0.527" | 0.545" | 0.569" |
| 5/8" | 0.750" (19.0 mm) | 0.652" | 0.666" | n/a |
| 3/4" | 0.875" (22.2 mm) | 0.745" | 0.785" | 0.811" |
| 1" | 1.125" (28.6 mm) | 0.995" | 1.025" | 1.055" |
| 1-1/4" | 1.375" (34.9 mm) | 1.245" | 1.265" | 1.291" |
| 1-1/2" | 1.625" (41.3 mm) | 1.481" | 1.505" | 1.527" |
| 2" | 2.125" (54.0 mm) | 1.959" | 1.985" | 2.009" |
| 2-1/2" | 2.625" (66.7 mm) | 2.435" | 2.465" | 2.495" |
| 3" | 3.125" (79.4 mm) | 2.907" | 2.945" | 2.981" |
| 3-1/2" | 3.625" (92.1 mm) | 3.385" | 3.425" | 3.459" |
| 4" | 4.125" (104.8 mm) | 3.857" | 3.905" | 3.935" |
| 5" | 5.125" (130.2 mm) | 4.805" | 4.875" | 4.907" |
| 6" | 6.125" (155.6 mm) | 5.741" | 5.845" | 5.881" |
| 8" | 8.125" (206.4 mm) | 7.583" | 7.725" | 7.785" |
| 10" | 10.125" (257.2 mm) | 9.449" | 9.625" | 9.701" |
| 12" | 12.125" (308.0 mm) | 11.315" | 11.565" | 11.617" |
Copper Development Association, Tables 14.2a-c (nominal dimensions). n/a: the CDA lists no Type M tube in that size.
| Size | Type K wall | Type L wall | Type M wall |
|---|---|---|---|
| 1/4" | 0.035" | 0.030" | n/a |
| 3/8" | 0.049" | 0.035" | 0.025" |
| 1/2" | 0.049" | 0.040" | 0.028" |
| 5/8" | 0.049" | 0.042" | n/a |
| 3/4" | 0.065" | 0.045" | 0.032" |
| 1" | 0.065" | 0.050" | 0.035" |
| 1-1/4" | 0.065" | 0.055" | 0.042" |
| 1-1/2" | 0.072" | 0.060" | 0.049" |
| 2" | 0.083" | 0.070" | 0.058" |
| 2-1/2" | 0.095" | 0.080" | 0.065" |
| 3" | 0.109" | 0.090" | 0.072" |
| 3-1/2" | 0.120" | 0.100" | 0.083" |
| 4" | 0.134" | 0.110" | 0.095" |
| 5" | 0.160" | 0.125" | 0.109" |
| 6" | 0.192" | 0.140" | 0.122" |
| 8" | 0.271" | 0.200" | 0.170" |
| 10" | 0.338" | 0.250" | 0.212" |
| 12" | 0.405" | 0.280" | 0.254" |
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Copper tube size and the nominal size
The same rule makes 3/4" copper 0.875" (7/8") across and 1" copper 1.125". This sizing is called copper tube size (CTS). PEX and CTS CPVC are made to it too, so 1/2" PEX and 1/2" CTS CPVC are also 0.625" across.
SharkBite sizes its push-to-connect fittings by CTS, so a 1/2" fitting takes copper, CTS CPVC or PEX of that size. PVC and steel use iron pipe size, which is wider: see the PVC pipe size chart.
Type K, L and M
Type K has the thickest wall and Type M the thinnest, at every size. Rigid copper is printed in a color for its type: green for K, blue for L, red for M, and yellow for DWV drain tube. For how the types are used, see Type L vs Type M copper.
DWV copper
Copper drain, waste and vent tube has the same outside as the other types at each size and a thinner wall.
| Size | Outside (OD) | Inside (ID) | Wall |
|---|---|---|---|
| 1-1/4" | 1.375" | 1.295" | 0.040" |
| 1-1/2" | 1.625" | 1.541" | 0.042" |
| 2" | 2.125" | 2.041" | 0.042" |
| 3" | 3.125" | 3.030" | 0.045" |
| 4" | 4.125" | 4.009" | 0.058" |
| 5" | 5.125" | 4.981" | 0.072" |
| 6" | 6.125" | 5.959" | 0.083" |
| 8" | 8.125" | 7.907" | 0.109" |
Copper Development Association, Table 14.2d. DWV starts at 1-1/4".
ACR tube
Copper tube for air conditioning and refrigeration (ACR) is named by its actual outside diameter. 3/8" ACR tube is 0.375" across, the outside of 1/4" plumbing tube, and 7/8" ACR is the outside of 3/4" plumbing tube.
Measuring copper pipe
Measure across the outside with a caliper and take 1/8" off to get the size. For one size across every kind of pipe, see the 1/2", 3/4" and 1" pipe OD pages.