Inside Diameter

Published: August 23, 2018 | Last updated: July 5, 2023

What Does Inside Diameter Mean?

The inside diameter (ID) of a hollow circular object, like a pipe, is a measurement of the distance of a straight line from one point on the inner wall of the object, through its center, to an opposite point also on the inside. The inside diameter is dependent on the outside diameter of the object and its wall thickness.

Inside diameter is also known as inner diameter or internal diameter.


Trenchlesspedia Explains Inside Diameter

The inside diameter of a pipe is calculated by subtracting twice the pipe’s wall thickness from the total external diameter. This calculation removes the pipe’s walls from the measurement, leaving only the inside diameter.

Inside diameter measurements are crucial for flow and volumetric calculations. The inside diameter of sewer pipes, for instance, must be large enough to accommodate the expected flow rates and volumes. Inadequate inside diameters can result in backups and possible pipe failure.

In trenchless construction, inside diameters are measured to determine the appropriate size and type of pipeline rehabilitation required. For example, cured-in-place-pipe liners must be adequately sized to ensure that the liner and resin make proper contact with the pipe’s inner walls.



Inner Diameter

Internal Diameter

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