Pipe Volume Calculator
Water or any liquid in a pipe from inside diameter (or OD and wall) and length: litres, gallons, ft³, mass at your density, per metre and per foot, or segments.
Internal volume in L, m³, US and imperial gallons and ft³, the mass of the liquid at the density you set, volume per metre and per foot, cross-section, and a table for segments typed one per line.
Example: 100 mm bore over 25 m holds 196 L (51.9 US gal) — 7.85 L per metre — and 196 kg of water; 4.5 in OD with a 0.237 in wall over 100 ft (4.026 in inside) holds 66.1 gal, 0.661 gal per foot.
A cylinder,
by the inside diameter.
How the bore is read, what the units mean, and why nominal sizes are not converted.
The volume
A pipe holds π × (d/2)² × L, with d the inside diameter. If you know the outside diameter and the wall, the bore is OD − 2 × wall. Several runs can be typed one per line — "name, diameter, length" with a unit after each number (mm, cm, m, in, ft; " for inches) — and are summed; without a unit the defaults from the fields apply. Volume is converted with the exact factors 1 m³ = 1 000 L = 264.172 US gal = 219.969 imperial gal = 35.3147 ft³.
Mass and per-length
The liquid's mass is volume × density; 998 kg/m³ is water at 20 °C and the field takes any other liquid (glycol mixtures, oil, brine). A "% full" scales the volume as a share — the shape of a partly filled horizontal pipe by depth is the tank-volume tool's job. Per metre and per foot figures let you size a whole system from a schedule of lengths.
Nominal sizes
The page does not convert a nominal pipe size to an inside diameter on purpose: a "4-inch" pipe is 4.026 in inside in Schedule 40 steel, 4.5 in outside, and something else again in PVC, copper or PEX. Read the inside diameter from the pipe's data sheet or measure it and enter that. Nothing leaves the browser; the same four anonymous usage counts as the rest of the site apply.
SOURCES
- V = π(d/2)²·L with the inside diameter (OD − 2 × wall); 1 m³ = 1 000 L = 264.172 US gal = 219.969 imp gal = 35.3147 ft³; mass = V × density (water 998 kg/m³ at 20 °C, editable)
Last reviewed 22 September 2026. How results are checked: How we verify.