# Annular Capacity Calculator (Annular Volume)

Quickly calculate the available annular volume between two concentric pipes or cylinders with our easy-to-use Annular Capacity Calculator.

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## What is Annular Capacity?

Annular Capacity means the available space or volume between two circular surfaces, such as a pipe and the surrounding casing. Imagine you have a pipe running through the middle of a larger tube or pipe, the empty space between the inner pipe and the outer pipe or casing is called the ‘annular capacity’ or ‘annular volume’.

This annular capacity is important because it allows for the flow of fluids, gases or other materials around the inner pipe. The size or capacity of this annular space can be calculated and is a key factor in the design and operation of many industrial systems such as oil wells and chemical processing plants.

## How to Use Annular Capacity Calculator

• To use the annular capacity calculator, you need to know the inner diameter of the hole size and the outer diameter of the pipe.
• Input these data into the calculator in the respective units.
• Once you input the values, the calculator will automatically display the annular volume.

## What is the Formula to Calculate Annular Capacity?

• Dh is the inner diameter of the drill hole size (in inches).
• Dp is the outer diameter of the drill pipe (in inches).

## How to Calculate Annular Capacity?

Below is a simple explanation of calculating annular capacity with 2 example:

Example 1:

What is the annular capacity in barrels per foot (bbl/ft) if the inner pipe diameter is 4 inches and the outer casing diameter is 6 inches?

Solution :

Casing diameter (Dh) = 6 in
pipe diameter (Dp) = 4 in

Annular Capacity = (Dh2 – Dp2) ÷ 1029.4
Annular Capacity = (62 – 42) ÷ 1029.4
Annular Capacity = (36 – 16) ÷ 1029.4
Annular Capacity = (20) ÷ 1029.4
Annular Capacity = 0.0194287934719254 ≈ 0.02 bbl/ft

Example 2:

What is the annular capacity in barrels per foot (bbl/ft) if the inner pipe diameter is 8 inches and the outer casing diameter is 1 foot 2 inch?

Solution :

First, we need to convert the hole size value from feet and inches to inches.

1 ft 2 in = (1 x 12 inches) + 2 inches = 14 inches

Annular Capacity = (Dh2 – Dp2) ÷ 1029.4
Annular Capacity = (142 – 82) ÷ 1029.4
Annular Capacity = (196 – 64) ÷ 1029.4
Annular Capacity = (132) ÷ 1029.4
Annular Capacity = 0.1282300369147076 ≈ 0.13 bbl/ft

## Annular Capacity Reference Table

This annular capacity reference table provides key design data for common pipe size combinations used in various industries, including oil & gas, HVAC and plumbing. Use this quick reference to easily determine the annular capacity for your project needs.