Pipe Volume Calculator

Frequently Asked Questions

How many gallons in 50 feet of 4-inch pipe?

ID = 4 in, radius = 2 in = 0.1667 ft. Volume = pi x 0.1667^2 x 50 = 4.36 cu ft x 7.481 = 32.6 gallons.

What is the volume of a 6-inch pipe per foot?

pi x (3/12)^2 x 1 = 0.1963 cu ft/ft = 1.47 gallons per foot of 6-inch pipe.

How heavy is water in 100 ft of 2-inch pipe?

Volume = pi x (1/12)^2 x 100 = 2.18 cu ft = 16.3 gallons. Water weight = 16.3 x 8.34 = 136 lbs.

What is the formula for pipe volume?

Volume = pi x (inner_diameter_in / 24)^2 x length_ft in cubic feet. Multiply by 7.481 for gallons.

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Important Disclaimer: Estimates for informational purposes only.

This calculator provides estimates for informational purposes only. Results are based on assumptions and may not reflect actual outcomes. Consult qualified professionals in relevant fields before making important decisions based on these results.

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How This Calculator Works

The volume of a cylinder is pi x r^2 x length, where r is the inner radius in feet. The calculator converts the diameter from inches to feet, computes the cross-sectional area, multiplies by the pipe length, then converts to gallons (1 cu ft = 7.481 gallons). Weight is volume times the density of the selected material.

Formula: volume_cuft = pi x (d_in / 24)^2 x length_ft. Gallons = volume_cuft x 7.481.

Common Pipe Sizes and Capacities

Volume per foot of pipe (water capacity):

1 in pipe: 0.00341 cu ft/ft = 0.0255 gal/ft

2 in pipe: 0.01364 cu ft/ft = 0.102 gal/ft

3 in pipe: 0.03068 cu ft/ft = 0.230 gal/ft

4 in pipe: 0.05454 cu ft/ft = 0.408 gal/ft

6 in pipe: 0.12272 cu ft/ft = 0.918 gal/ft

8 in pipe: 0.21817 cu ft/ft = 1.632 gal/ft

12 in pipe: 0.49087 cu ft/ft = 3.672 gal/ft

These are internal diameter values. Actual pipe inner diameter depends on schedule (pipe schedule affects wall thickness). Schedule 40 PVC 4-in has an ID of 4.026 in.

Common Applications

Pipe volume calculations are used in several contexts:

Irrigation: total water stored in supply lines to size pumps and pressure tanks

Fire suppression: volume of wet-pipe sprinkler systems for antifreeze capacity

Concrete piers: volume of concrete in a sonotube form for bag count

Hydronic heating: total system volume for antifreeze and expansion tank sizing

Drainage: pipe volume to verify flow capacity against storm event volumes

FAQ

How many gallons in 100 feet of 2-inch pipe?

Inner radius = 1 in = 0.0833 ft. Volume = pi x 0.0833^2 x 100 = 2.18 cu ft x 7.481 = 16.3 gallons.

What is the difference between nominal and actual pipe diameter?

Nominal pipe size (NPS) is a conventional label, not the actual inner diameter. A 2-in Schedule 40 pipe has an inner diameter of 2.067 in, not exactly 2 in. For precise calculations use the actual inner diameter from a pipe specification table.

How much does a 100 ft run of 4-in pipe filled with water weigh?

Volume = pi x (2/12)^2 x 100 = 8.73 cu ft. Gallons = 8.73 x 7.481 = 65.3 gal. Water weight = 65.3 x 8.34 = 544 lbs. Add the pipe weight (about 10 lb/ft for Schedule 40 PVC) for total load.

Can I use this for rectangular ducts?

No. This calculator is for round pipes only. For rectangular ducts multiply width x height (in feet) x length to get cubic feet, then multiply by 7.481 for gallons if needed.

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