A completely filled straight pipe is a cylinder. Enter its inside diameter, liquid-filled length, count of identical runs and liquid density in pounds per US gallon to estimate contained gallons and pounds.

Formula: in³ per run = π × (inside diameter in ÷ 2)² × (liquid-filled ft × 12); US gal = in³ ÷ 231; lb = total US gal × liquid lb/US gal

Worked example

Two full, straight 100 ft runs with 4 in inside diameter contain about 130.56 US gal total. At an entered 8 lb per US gallon, the liquid weighs about 1,044.48 lb.

Inside diameter controls inventory

Nominal pipe size can differ from actual inside diameter. Measure or obtain the correct internal dimension for the installed pipe. The model assumes each run is completely full and straight for its entered liquid-filled length.

Do not infer density from gallons

The supplied liquid density controls pounds. Match its temperature and concentration to the contents. NIST defines one US liquid gallon as exactly 231 cubic inches, which provides the geometry-to-gallons step.

Fittings and partial fills are outside the model

Valves, elbows, tanks and hoses can add or subtract inventory; air pockets and partly filled horizontal runs also change the geometry. The result is a full-pipe liquid estimate, not a pressure, flow, spill or structural calculation.

Explore the related calculation

For a different starting point, try the vertical tank gallons and weight calculator or return to the main calculator. Browse the complete tool directory for this site.

Reference and corrections

The definitions and assumptions above follow these sources; the examples and calculator arithmetic are original to this page.

www.nist.gov reference

Found a problem? Email contact@gallonstopounds.org.

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