# Cross Sectional Area

Published: October 31, 2018 | Last updated: July 5, 2023

## What Does Cross Sectional Area Mean?

A cross sectional area is the area of the sliced portion of a 3D object, such as a pipe. When a pipe is sliced perpendicular to its longest axis, the cross sectional area will be calculated for the top part of the sliced portion, which is a circle. Calculating a cross-sectional area is an integral part of trenchless rehabilitation methods because based on this area, the size of the lining or replacement pipe is determined.

Cured-in-place pipe lining may require lesser change in cross sectional area of the host pipe than that would be required for the purpose of pipe bursting or sliplining. It's also used for calculating the flow rate of a pipe or pressure drop.

## Trenchlesspedia Explains Cross Sectional Area

The cross-sectional area of a pipe is calculated as A = π (Di ) 2 /4, where

A – area of the pipe

π – 3.14 (constant)

Di – Internal diameter of the pipe

The fluid carrying capacity of two pipes can be compared by using the ratio of their cross-sectional areas. By keeping the velocity constant, the flow capacity of different pipe sizes can be compared, which will be directly proportional to the change in diameter (D) of the pipe.

The internal diameter (ID) of the pipes should be used because the outer diameter (OD) of pipes are often kept constant for pipe fittings to fit. Pipes rated for higher pressure will have smaller ID but thicker pipe walls.