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Pipe Volume Calculator

Calculate pipe internal volume, fluid capacity in litres and gallons, volume per foot/meter, and water weight from inside diameter.

Internal liquid cavity
Engineering Note: Always use the inside diameter (ID), not outer diameter (OD), to calculate internal fluid capacity.
Pipe Cross-Section DiagramInside Dia (ID)Length (L)

V = π × (ID / 2)² × Length

Internal Pipe Capacity
Decimals:
Total Liquid CapacityLive Output
78.54 L
Additional Computed Dimensions
Linear Capacity (Metric)
7.854 L/m
Linear Capacity (Imperial)
0.632 gal/ft
Approx Water Weight
78.54 kg
Equivalent Standard Volume Units
US Gallons (gal)
20.748 us_gal
Cubic Feet (ft³)
2.774 ft3
Cubic Meters (m³)
0.079 m3
Imperial Gallons (UK gal)
17.276 imp_gal

Mathematical Formula & Step-by-Step Derivation

SI Normalized Math
General Formula:
V = π × (ID / 2)² × Length
Live Calculation With Your Input Values:
11. Pipe Volume Formula
Formula: V = π × (ID / 2)² × Length
Substituted: V = π × (10 cm / 2)² × (10 m)
Step Result: V = 78.54 L (20.748 US gal)

Internal cross-sectional area = 78.54 cm²

22. Linear Capacity & Water Weight
Formula: Linear Capacity = V / Length
Substituted: 7.854 L/meter (0.632 US gal/foot)
Step Result: Water Weight ≈ 78.54 kg (173.15 lbs)

Assumes standard pure water density (~1.0 kg/L). Slurries or dense liquids will weigh more.

How to Calculate Pipe Volume & Fluid Holding Capacity

A pipe or cylindrical tube is a hollow cylindrical conduit. Its fluid-carrying capacity depends strictly on its inside diameter (ID) and total run length. Outside diameter (OD) and pipe wall thickness must be accounted for to find the true internal bore.

  1. Measure Internal Bore (ID): Always use inside diameter. If only outer diameter (OD) and wall thickness (WT) are known: ID = OD − (2 × WT).
  2. Calculate Internal Radius: Radius r = ID ÷ 2.
  3. Compute Cross-Sectional Area: Area = π × r².
  4. Multiply by Pipe Run Length: Volume = Area × Length.
  5. Determine Capacity & Water Weight: Convert volume to litres (1 m³ = 1,000 L) or US gallons (1 m³ = 264.172 gal). Water weighs 1 kg per Liter (~8.34 lbs per US gallon).

Pipe Volume Formulas & Linear Capacity

Pipe Volume Formula:

V = π × (ID ÷ 2)² × Length

Capacity Per Meter:Litres/meter = π × (ID_m ÷ 2)² × 1,000
Capacity Per Foot:Gallons/foot = (π × r_in² × 12) ÷ 231

Worked Example: 4-Inch Nominal Schedule 40 Pipe (30m Run)

Specifications: A 4-inch nominal schedule 40 PVC pipe has an inside diameter of 10.23 cm (0.1023 m) and runs for 30 meters.

1. Inside Radius r = 0.1023 m ÷ 2 = 0.05115 m

2. Internal Cross-Section Area = π × (0.05115 m)² ≈ 0.00822 m²

3. Total Internal Volume = 0.00822 m² × 30 m = 0.2466 m³

4. Fluid Capacity in Litres = 0.2466 m³ × 1,000 = 246.60 Litres

5. Fluid Capacity in US Gallons = 246.60 ÷ 3.78541 ≈ 65.15 US Gallons

6. Water Weight in Pipe = 246.60 kg (~543.6 lbs)

Practical Notes & Guidelines

Schedule & Wall Thickness: Heavy schedule pipes (such as Schedule 80 steel or SDR 11 HDPE) have much thicker walls than Schedule 40, which significantly narrows inside diameter and fluid volume. Always look up actual internal diameter specs.

Related Calculators: For cylindrical storage vessels and dip measurements, use the Tank Volume Calculator, or calculate geometric cylinder values with our Cylinder Volume Calculator.

Frequently Asked Questions

How do I calculate the volume inside a pipe?▼
Calculate the internal circular area from the inside diameter: Area = π × (ID / 2)², then multiply by total pipe length: Volume = Area × Length.
Should I use pipe inside diameter or outside diameter?▼
Always use the inside diameter (ID). The pipe wall thickness occupies space; using outside diameter will falsely overestimate fluid capacity.
How many litres of water are in a pipe?▼
Multiply internal cross-sectional area (in square meters) by length (in meters) and multiply by 1,000 to get total Litres.
How do I calculate pipe capacity per meter?▼
Calculate volume for a 1-meter length: Litres per meter = π × (ID in meters / 2)² × 1,000. For example, a 50 mm (0.05 m) ID pipe holds π × (0.025)² × 1,000 ≈ 1.963 Litres per meter.
How do I calculate pipe volume per foot?▼
Calculate volume for a 12-inch length: Gallons per foot = (π × [ID in inches / 2]² × 12) ÷ 231. For example, a 2-inch ID pipe holds ~0.1632 US gallons per linear foot.
How do I convert pipe volume to gallons?▼
If internal volume is calculated in cubic inches, divide by 231 to obtain US liquid gallons. If in Litres, divide by 3.78541.
How much does the water inside a pipe weigh?▼
Water weighs exactly 1 kilogram per Liter (1,000 kg/m³) or approximately 8.34 pounds per US liquid gallon. Multiply total pipe litres by 1.0 kg (or gallons by 8.34 lbs).

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