A pipe volume calculator determines the internal capacity of cylindrical pipes. Enter the inner diameter (or radius) and pipe length to find how much liquid the pipe holds.
Pipe volume is the amount of space inside a cylindrical pipe, measured using the inner diameter and length. This determines how much water, gas, or other fluid the pipe can carry. Pipe volume is a direct application of the cylinder volume formula V = πr²h.
Plumbers, engineers, and contractors calculate pipe volume for water system design, drainage planning, fluid flow calculations, and estimating how much fluid is needed to fill a pipeline.
Pipe volume = π × (inner diameter/2)² × length.
Always use the inner diameter (ID), not the outer diameter (OD). The pipe wall thickness reduces the usable volume.
Example: A 4-inch (10.16 cm) inner diameter pipe, 100 feet (30.48 m) long:
V = π × 5.08² × 3048 = 247,300 cm³ = 247.3 liters = 65.3 US gallons.
ID 1.6 cm, length 15.24 m: V = π×0.8²×1524 = 3,063 cm³ = 3.06 L = 0.81 gal.
ID 2.5 cm, length 20 m: V = π×1.25²×2000 = 9,817 cm³ = 9.82 L.
ID 15.24 cm, 30.48 m: V = π×7.62²×3048 = 556,180 cm³ = 556.2 L = 146.9 gal.
ID 61 cm, length 1000 m: V = π×0.305²×1000 = 292.25 m³ = 292,247 L.
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Answers to common questions about the pipe volume calculator.
V = π × (ID/2)² × length where ID = inner diameter. Use centimeters for result in cm³ (÷1000 for liters), or inches for in³ (÷231 for US gallons).
ID = inner diameter (the open space inside). OD = outer diameter (including wall thickness). For volume calculations, always use ID. ID = OD - 2×(wall thickness).
Wall volume = π × L × (R_outer² - R_inner²). This gives the volume of the pipe material itself, useful for calculating weight.
For a 1-inch ID pipe: V = π×0.5²×12 = 9.42 in³/foot = 0.041 gallons/foot. For 2-inch: 0.163 gal/ft. For 4-inch: 0.653 gal/ft.
Volume ÷ fill time = flow rate. Example: 100 L pipe fills in 5 minutes = 20 L/min flow rate. Or use Q = A × v (cross-sectional area × flow velocity).