Pipe Volume Calculator
A pipe is a cylinder, so its volume is the bore area times the length. Enter the inside diameter and length for the gallons it holds — handy for flushing, chlorinating, or filling a line.
Volume
8.16gallons
- Volume
- 1.091 cu ft
- Volume
- 30.9 liters
How it’s calculated
Volume = π × radius² × length. The radius in feet is the inside diameter in inches ÷ 24 (halve it, then ÷ 12 to feet). That gives cubic feet; multiply by 7.48 for US gallons, or by 3.785 more for liters.
Worked example
A 2-inch inside-diameter pipe, 50 ft long: radius = 2 ÷ 24 = 0.083 ft; π × 0.083² × 50 ≈ 1.09 cu ft; × 7.48 ≈ 8.16 gallons.
FAQs
- Should I use the inside or outside diameter?
- Inside diameter — the actual bore that holds water — not the nominal pipe size and not the outside diameter. A nominal “2-inch” pipe isn't 2 inches inside (Schedule 40 PVC is about 2.05 in, type-L copper about 1.99 in), and the OD is larger still. Look up the true ID for your pipe's material and schedule.
- What's this useful for?
- Knowing the water a line holds — for shock-chlorinating a well or new plumbing, flushing or winterizing, sizing how much antifreeze a run needs, or estimating how long a pipe takes to drain.
- Does this give flow rate?
- No — this is the static volume the pipe holds, not how fast water moves through it. Flow depends on pressure, pipe size, and length, which is a different calculation.
Sources
- Volume = π × radius² × length (cylinder). Radius_ft = diameter_in ÷ 24. 7.48052 US gal/cu ft and 3.785411784 L/gal (both exact).