Pipe Volume Calculator
Calculate pipe volume accurately for your build. Get material quantities, waste allowances, and project cost breakdowns.
Formula
Volume = pi x (d/2)^2 x L | Gallons = Volume (cu in) / 231
The volume of a pipe (cylinder) is pi times the radius squared times the length. The inside diameter is used to determine flow capacity. Divide cubic inches by 231 to get US gallons, or by 1,728 to get cubic feet. Multiply gallons by 8.34 to get the weight of water in pounds.
Worked Examples
Example 1: Residential Water Line Volume
Problem: Calculate the volume of water in a 2-inch diameter pipe that is 100 feet long.
Solution: Radius = 2/2 = 1 inch\nVolume = pi x 1^2 x 1200 = 3,769.91 cu in\nGallons = 3,769.91 / 231 = 16.32 gal\nWeight = 16.32 x 8.34 = 136.12 lbs
Result: 16.32 gallons (136.12 lbs of water)
Example 2: Fire Sprinkler Main Volume
Problem: How many gallons are in 250 feet of 4-inch pipe?
Solution: Radius = 4/2 = 2 inches\nLength = 250 x 12 = 3000 inches\nVolume = pi x 4 x 3000 = 37,699.1 cu in\nGallons = 37,699.1 / 231 = 163.2 gal
Result: 163.2 gallons (1,361.1 lbs of water)
Frequently Asked Questions
How do you calculate the volume of water in a pipe?
The volume of a pipe is calculated using the cylinder formula: V = pi x r^2 x L, where r is the inside radius and L is the length. First convert the diameter to inches and divide by 2 to get the radius. Multiply pi times the radius squared times the length in inches to get cubic inches. Divide by 231 to convert to US gallons, or by 1,728 to get cubic feet. Always use the inside diameter of the pipe, not the outside diameter, since wall thickness reduces the actual flow area.
What is the inside diameter of common pipe sizes?
Nominal pipe sizes do not match actual inside diameters. A 1/2 inch nominal copper pipe has an inside diameter of about 0.545 inches. A 3/4 inch pipe is about 0.785 inches inside. A 1-inch PVC Schedule 40 pipe has a 1.029-inch inside diameter. A 2-inch pipe is about 2.067 inches inside, and a 4-inch pipe is about 4.026 inches. For accurate volume calculations, always look up the actual inside diameter for the specific pipe material and schedule you are using.
How many gallons of water are in 100 feet of 1-inch pipe?
Using the standard 1-inch Schedule 40 pipe with an inside diameter of 1.029 inches, the volume is pi x (0.5145)^2 x 1200 = 997.7 cubic inches. Dividing by 231 gives approximately 4.32 US gallons per 100 feet. This is useful for calculating purge volumes when flushing pipes, estimating water hammer effects, or determining how much antifreeze is needed to winterize a plumbing system.
How much does water in a pipe weigh?
Water weighs 8.34 pounds per US gallon at standard temperature. To find the weight of water in a pipe, first calculate the volume in gallons using the pipe diameter and length, then multiply by 8.34. For example, a 4-inch pipe 200 feet long holds about 130 gallons, which weighs approximately 1,084 pounds. This weight must be accounted for when designing pipe supports, hangers, and structural mounts, especially for large-diameter or long runs.
Is my data stored or sent to a server?
No. All calculations run entirely in your browser using JavaScript. No data you enter is ever transmitted to any server or stored anywhere. Your inputs remain completely private.
What formula does Pipe Volume Calculator use?
The formula used is described in the Formula section on this page. It is based on widely accepted standards in the relevant field. If you need a specific reference or citation, the References section provides links to authoritative sources.