How do I calculate the volume inside a pipe?

Volume = π × r² × length, where r is the inside radius (diameter ÷ 2). For example, a 4-inch diameter pipe (2-inch radius) that's 10 feet long: 3.14 × 4 × 120 = 1,507 cubic inches, or 6.5 gallons.

Should I use inside or outside diameter for calculations?

Always use inside diameter (ID) for volume calculations since you're measuring the space inside the pipe. Outside diameter (OD) is used for fitting clearances and structural calculations. Pipe thickness affects the difference.

How do I convert pipe volume to gallons?

Calculate volume in cubic inches, then divide by 231 (cubic inches per gallon). Or calculate in cubic feet and multiply by 7.48 (gallons per cubic foot). This helps determine water capacity for plumbing systems.

Why do I need to know pipe volume?

Pipe volume calculations are essential for determining system capacity, drainage rates, water treatment chemical dosing, freeze protection calculations, pump sizing, and understanding flow rates in plumbing and irrigation systems.

Home & Construction

Pipe Volume

Calculate volume capacity of pipes and tubes.

Unit System

Inner Diameter (inches)

Length (feet)

Enter pipe dimensions

How to Use This Calculator

Measure Pipe Dimensions

Determine the inside diameter of the pipe (not outside diameter) and the length of the pipe run. Make sure both measurements use the same units.

Enter Values

Input the inside diameter and pipe length. Choose your preferred input units (inches, feet, centimeters, etc.). The calculator will handle conversions.

Calculate Volume

The calculator shows volume in multiple units: cubic inches, cubic feet, gallons, and liters. This helps you understand capacity regardless of your project needs.

Apply to Your System

Use the volume calculation for water system design, chemical dosing, drainage planning, or understanding how much water your pipes hold for freeze protection considerations.