Pipe Volume Calculator
Find how much water a pipe holds and how much it weighs. Enter the inner diameter and length in any unit — results in gallons, liters, cubic feet, pounds, and kilograms.
What is a pipe volume calculator?
A pipe volume calculator tells you exactly how much fluid fits inside a pipe. Give it the inner diameter and the length of the pipe, and it returns the internal volume in gallons, liters, cubic inches, and cubic feet — plus the weight of water if the pipe is fully filled. No manual math, no unit confusion.
Plumbers use it to size supply lines. Irrigation designers use it to plan flow capacity. Homeowners use it to figure out how long a garden hose takes to fill a pond. Engineers use it to estimate the structural load a water-filled pipe adds to a building. The calculation is the same in every case: the volume of a hollow cylinder.
This tool lives in the CalcMora Converters section because it converts physical pipe dimensions into volume and weight values — the same way the kg to lbs calculator converts between weight units, or the currency converter switches between monetary values. If you work with color codes or number systems in your projects, the color converter and the hex to decimal converter are also in the same section.
Pipe volume formula
A pipe is a hollow cylinder. The volume of any cylinder is the area of the circular cross section multiplied by the length. For a pipe, you use the inner diameter because the pipe wall itself holds no fluid.
Volume = π × (d ÷ 2)² × L
Where d is the inner diameter of the pipe and L is the length. The result is in cubic units matching your input — cubic inches if you enter inches, cubic meters if you enter meters, and so on.
To get water weight from volume, multiply by the density of water. Fresh water weighs approximately 8.34 pounds per US gallon or 1 kilogram per liter. This calculator applies those conversions automatically so you see both volume and weight in one step.
Volume in gallons
gallons = cubic inches ÷ 231
One US gallon is exactly 231 cubic inches by definition.
Water weight in pounds
lbs = gallons × 8.34
Fresh water at room temperature weighs 8.34 lb per US gallon.
How to use this pipe volume calculator
Measure or look up the inside diameter of the pipe. Choose your unit from the dropdown — inches, feet, mm, cm, or meters all work.
Enter how long the pipe is. You can use a different unit than the diameter — the calculator handles the conversion.
The result appears in six formats: cubic inches, cubic feet, liters, US gallons, and water weight in both pounds and kilograms.
Use the Copy button to grab the result as text, or share it directly from the calculator.
Worked examples
Example 1: 2-inch pipe, 50 feet long
A standard 2-inch inner diameter pipe running 50 feet holds about 8.16 gallons of water, which weighs roughly 68 pounds. This is a common size for residential cold water supply lines.
Example 2: 100mm pipe, 10 meters long
A 100mm inner diameter pipe that is 10 meters long holds about 78.5 liters of water, weighing roughly 78.5 kg. This is a typical size for main drainage or commercial water supply runs.
Example 3: Garden hose, ¾ inch, 25 feet
A ¾-inch inner diameter garden hose that is 25 feet long holds about 0.57 gallons. Knowing this helps you understand the lag time before fresh water reaches the end of a long hose run.
Example 4: Large irrigation main, 6 inch, 200 feet
A 6-inch inner diameter irrigation main running 200 feet holds about 293 gallons of water, weighing over 2,440 pounds. This weight estimate matters when calculating structural support for overhead pipe runs.
Common pipe sizes and their water capacity
The table below shows approximate water volume and weight per foot of pipe for common imperial pipe sizes. These figures assume the pipe is fully filled with fresh water.
| Inner Diameter | Volume per foot | Gallons per foot | Weight per foot (lbs) |
|---|---|---|---|
| ½ inch | 2.36 in³ | 0.0102 gal | 0.085 lbs |
| ¾ inch | 5.30 in³ | 0.0229 gal | 0.191 lbs |
| 1 inch | 9.42 in³ | 0.0408 gal | 0.341 lbs |
| 1½ inch | 21.2 in³ | 0.0918 gal | 0.766 lbs |
| 2 inch | 37.7 in³ | 0.163 gal | 1.36 lbs |
| 3 inch | 84.8 in³ | 0.367 gal | 3.07 lbs |
| 4 inch | 150.8 in³ | 0.653 gal | 5.45 lbs |
| 6 inch | 339.3 in³ | 1.47 gal | 12.3 lbs |
For metric pipe sizes, use the calculator directly — enter the diameter in millimeters and the length in meters to get results in liters and kilograms instantly.
Pipe volume calculator FAQ
What is the formula for pipe volume?
The volume of a pipe is calculated using the cylinder volume formula: V = π × (d/2)² × L, where d is the inner diameter and L is the length of the pipe. The result is the internal volume — the space available for fluid. Always use the inner diameter, not the outer diameter, for accurate results.
Should I use inner diameter or outer diameter?
Always use the inner diameter. The outer diameter includes the pipe wall thickness, which holds no fluid. Using the outer diameter will give you a larger number that overstates the actual capacity. If you only know the outer diameter, subtract twice the wall thickness to get the inner diameter.
How do I find the volume of water in a pipe in gallons?
Calculate the volume in cubic inches first using the formula V = π × (d/2)² × L, then divide by 231 to convert to US gallons. For example, a 2-inch inner diameter pipe that is 10 feet long holds about 1.63 gallons. This calculator shows the result in cubic inches, cubic feet, liters, and gallons automatically.
How much does water in a pipe weigh?
Water weighs approximately 8.34 pounds per US gallon, or 1 kilogram per liter. Once you know the volume of the pipe, multiply by the density of water to get the weight. This calculator does that automatically and shows the water weight in both pounds and kilograms.
Can I use this calculator for pipes in metric units?
Yes. This calculator accepts millimeters, centimeters, and meters for both diameter and length. You can mix units — for example, enter diameter in millimeters and length in meters — and the calculator converts everything before calculating. Results are shown in both metric and imperial units.
Does pipe length affect volume proportionally?
Yes, pipe volume scales directly with length. If you double the length of a pipe while keeping the same diameter, the volume doubles. Diameter has a squared effect — doubling the diameter multiplies the volume by four. This is why pipe diameter matters much more than length when sizing pipes for high-flow applications.
What is this calculator useful for?
This calculator helps with home plumbing, irrigation design, heating systems, pool and pond filling, industrial pipeline planning, and any situation where you need to know how much fluid a pipe can hold. It is also useful for estimating the weight load that a filled pipe adds to a structure.
This tool is for educational purposes only. Always verify important results with a qualified professional.
