Pipe Volume Calculator uses V = πr²L to find internal pipe capacity from diameter or radius and length, then shows gallons, liters, cubic volume, cross-section area, circumference, and water weight.
The Pipe Volume Calculator determines internal pipe capacity from the inner diameter or inner radius and the pipe length. Enter your pipe dimensions and the tool returns the total internal liquid volume, cubic space volume across multiple unit systems, cross-section area and inner circumference, and an estimated weight for a freshwater-filled pipe. Results are shown in US gallons or liters, cubic feet, cubic meters, cubic yards, and both imperial and metric weight.
Pipe volume formula
Internal pipe volume is calculated using the standard geometric cylinder formula:
When inner diameter is entered, the radius is derived before the formula is applied:
In US Customary mode, pipe size is in inches and length in feet. In metric mode, pipe size is in millimeters and length in meters. The calculator converts both values into consistent units before applying the formula, then expresses results in US gallons, liters, UK gallons, cubic feet, cubic meters, cubic yards, and an estimated filled-water weight.
Calculator inputs
Measurement System
Select US Customary or Metric. This sets the unit labels for all other inputs and determines which conversion path runs before the formula is applied. Switching systems recalculates all outputs automatically.
Dimension Type
Choose whether the value you are entering is the inner diameter or the inner radius. If diameter is selected, the tool divides it by two before applying the formula. Either way, the value must be the internal bore — the opening the liquid passes through.
Pipe Dimension Size
The numeric measurement of the inner diameter or inner radius — in inches for US mode or millimeters for metric mode. This must be the internal dimension. Nominal pipe sizing and outside diameter are not the same as internal bore; confirm the internal measurement before entering.
Pipe Length
The length of the internal pipe section that will be filled with liquid — feet (US) or meters (metric). Enter only the length that is actually filled. Dry sections, trapped air, or fitting void spaces should be excluded unless their internal volume is intentionally included.
What each result shows
Total Internal Capacity
The primary output — the total liquid volume that can be contained within the pipe at the entered dimensions. Displayed in US gallons when US Customary mode is active, or in liters in metric mode. Use this value when determining fill volume, system sizing, hydrostatic test volume, or fluid hold-up capacity.
Alternative Liquid
The same total capacity in the other primary liquid unit — liters if US mode was used, US gallons if metric was used. Also includes UK gallons for international reference. These values represent the same volume in different measurement conventions, not different fluid types.
Cubic Space Volume
The geometric displacement of the pipe interior in cubic units. The primary result — cubic feet (US) or cubic meters (metric) — is shown alongside both cubic meters and cubic yards. Use these when the required format is volumetric displacement rather than liquid measurement units.
Cross-Section Profile
The internal circular opening area — square inches (US) or square centimeters (metric) — plus the converted area in the alternate unit system and the inner circumference. These values come from the inner radius using standard circle geometry and are independent of pipe length.
Estimated Water Weight
The mass of standard fresh water required to completely fill the pipe at the calculated volume. Shown in pounds (US primary) and kilograms. Uses a freshwater density baseline near 60°F / 15°C. Actual weight will differ for other liquids, elevated temperatures, dissolved solids, or partial fill.
Example: 2‑inch pipe, 100 feet
A 2-inch inner diameter produces a radius of 1 inch. The calculator converts 1 inch to feet (0.08333 ft), applies π × (0.08333)² × 100, then converts the resulting cubic footage to all output units.
Calculation assumptions and limits
What this calculator does not account for
- The calculator requires the internal pipe dimension — not nominal size or outside diameter. Confirm internal bore before entering a value; these often differ significantly from nominal designations.
- Pipe length must equal the filled internal length. Exclude any section that is dry, partially filled, or occupied by internal fittings unless that void volume is deliberately included in the entered dimensions.
- Water weight assumes the pipe is completely full along its entered length. Partial fill produces a proportionally lower actual weight.
- Fittings, bends, wall thickness variation, slope, trapped air, and internal pressure changes are not modeled. They affect real-world capacity only if already reflected in the entered internal dimensions.
- Pressurized gases and compressible chemicals require separate engineering calculations. Volume at atmospheric conditions is not the same as usable capacity under pressure, where compressibility and system pressure determine the actual quantity present.