Free Plumbing Tool
Pipe Volume Calculator
Enter pipe size and length to instantly get volume in gallons, cubic feet, and liters. Add an optional flow rate to calculate fill time. Includes a full Schedule 40 pipe volume reference table.
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Calculate Pipe Volume
Select a Schedule 40 pipe size or enter a custom inner diameter. Add length and an optional flow rate for fill time. Results update instantly.
Based on Schedule 40 inner diameter. Use “Enter inner diameter” for other schedules.
Enables fill time calculation.
Volume results
Gallons (US)
17.43
Cubic feet
2.33
Liters
65.99
Fill time
Enter GPM above
Inner diameter used
2.067"
Gallons per foot
0.1743
Cubic inches total
4,026.7
Schedule 40 Pipe Volume Reference Table
Gallons and liters per linear foot for standard Schedule 40 pipe sizes. Use these values to quickly estimate system volume without entering each run individually.
Why does pipe volume matter on the job?
Pipe volume drives several critical decisions: sizing expansion tanks for hydronic systems, calculating glycol and chemical treatment doses, pressure-testing line segments, and estimating fill and flush times for commissioning.
For glycol-filled systems, the industry rule of thumb is to move at least two full pipe volumes during a flush to fully remove the old fluid. Underestimating volume means undertreated or inadequately flushed systems — and callbacks.
Schedule 40 vs Schedule 80: volume difference
Schedule 80 pipe has thicker walls and a smaller inner diameter than Schedule 40 of the same nominal size. A nominal 2“ Schedule 80 pipe has an ID of 1.939“ vs 2.067“ for Schedule 40 — about 12% less volume per foot.
For accurate results on Schedule 80 or other non-standard schedules, switch to “Enter inner diameter” mode above and type in the actual ID from the pipe spec sheet or manufacturer data.
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Common Questions About Pipe Volume
How do you calculate the volume of a pipe?
Pipe volume = π × (inner radius)² × length. Find the pipe's inner diameter, halve it to get radius, square it, multiply by π (3.14159), and multiply by pipe length in inches. Divide by 231 to convert cubic inches to US gallons, or by 1728 for cubic feet. This calculator handles the math — just enter size and length.
What is the difference between nominal pipe size and inner diameter?
Nominal pipe size is a standardized label, not the actual measurement. A nominal 2" Schedule 40 pipe has an outer diameter of 2.375" and an inner diameter of 2.067". Wall thickness varies by schedule: Schedule 80 is thicker, so the ID is smaller and volume per foot is less. Always use actual inner diameter for volume calculations.
How many gallons are in a 100-foot run of 2-inch pipe?
A 100-foot run of 2-inch Schedule 40 pipe (ID 2.067") holds approximately 17.4 gallons. Schedule 80 of the same nominal size (ID 1.939") holds about 15.3 gallons.
How do I calculate how long it takes to fill a pipe?
Divide pipe volume in gallons by flow rate in GPM. A pipe holding 17.4 gallons at a 5 GPM supply takes 3.5 minutes to fill. Use this calculator's flow rate field to get fill time automatically.
Why does pipe volume matter for plumbing contractors?
Pipe volume drives expansion tank sizing, chemical and glycol dosing, pressure test planning, and flush duration. Underestimating volume leads to undersized expansion tanks, undertreated systems, and incomplete flushes — all of which cause callbacks.
How much does pipe schedule affect volume?
Significantly for large pipe. A nominal 4" Schedule 40 pipe (ID 4.026") holds 0.660 gal/ft; Schedule 80 (ID 3.826") holds about 0.597 gal/ft — 10% less. Use the custom ID field in this calculator for non-Schedule-40 pipe.
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Book a Free DemoVolume calculations are based on Schedule 40 inner diameters per ASME B36.10M unless a custom inner diameter is entered. Verify specifications against actual pipe data sheets before use in system design.