Work out how much fluid a length of pipe or tubing holds (capacity), how much it displaces, and its steel volume — all from the OD and ID.
Capacity is how much fluid the inside of the pipe holds per foot — you need it for pill volumes, displacement volumes, and how many barrels to pump to fill or circulate the string. Displacement is the volume of steel in the pipe wall — the fluid the pipe pushes out of the way when you run it, which is what moves the pit level as you trip in.
Both come straight from the diameters. Capacity uses the ID; displacement uses the difference between OD and ID (the metal).
ID and OD in inches. The constant 1029.4 converts square inches of area per foot into barrels per foot. Multiply either by length (ft) to get a total in barrels.
Uses nominal ID. Real drift or worn ID will differ slightly — for tight-tolerance work use the actual measured ID.
For 5" OD casing with a 4.276" ID: capacity = 4.276² / 1029.4 = 0.01776 bbl/ft; displacement = (5² − 4.276²) / 1029.4 = 0.00653 bbl/ft. Over a 1,000 ft string that is 17.76 bbl of internal capacity.
Completion and workover engineering support — tubular selection, load cases and more.