Pipe Volume Calculator
Capacity in gallons, litres and cubic feet — from inner diameter or nominal size and schedule, using the actual bore, full or partially filled.
Your pipe
Volume
66.13 US gal
- Litres
- 250.33 L
- Cubic feet
- 8.84 ft³
- Inner diameter
- 4.026 in
- Inner diameter is the actual bore from ASME B36.10M, not the nominal pipe size. Schedule changes the wall thickness and therefore the bore.
How this is calculated
Radius
inner diameter ÷ 2 ÷ 12 (to feet)
= 4.026 ÷ 2 ÷ 12
0.1678 ft
Cross-section area
π × r²
= π × 0.1678²
0.0884 ft²
Volume
cross-section area × length
= 0.0884 × 100
8.84 ft³ = 66.13 US gal = 250.33 L
How much water does a pipe hold?
Volume is the cross-section area times the length. For a pipe with a 4 inch inner diameter, the radius is 2 in = 0.1667 ft, so π × 0.1667² = 0.0873 ft². Over 100 ft that is 8.73 ft³ = 65.3 US gallons (247.3 L). For a partially full horizontal pipe, the tool uses the circular-segment area of the filled cross-section instead of the full circle.
Nominal pipe size vs actual inner diameter (steel, ASME B36.10M)
| Nominal (NPS) | Outside dia (in) | Sch 40 ID (in) | Sch 80 ID (in) |
|---|---|---|---|
| 1/2 | 0.840 | 0.622 | 0.546 |
| 3/4 | 1.050 | 0.824 | 0.742 |
| 1 | 1.315 | 1.049 | 0.957 |
| 1-1/2 | 1.900 | 1.610 | 1.500 |
| 2 | 2.375 | 2.067 | 1.939 |
| 3 | 3.500 | 3.068 | 2.900 |
| 4 | 4.500 | 4.026 | 3.826 |
| 6 | 6.625 | 6.065 | 5.761 |
Pipe volume per 100 ft (full, by inner diameter)
| Inner diameter | Cubic feet | US gallons |
|---|---|---|
| 1 in | 0.55 | 4.08 |
| 2 in | 2.18 | 16.32 |
| 3 in | 4.91 | 36.72 |
| 4 in | 8.73 | 65.28 |
| 6 in | 19.63 | 146.88 |
Plumbing tools
Common pipe volume mistakes
- •Using the nominal size as the bore. A “4 inch” Schedule 40 pipe has a 4.026 in actual inner diameter; Schedule 80 is 3.826 in. This tool uses the real bore from ASME B36.10M.
- •Using diameter instead of radius. Volume uses the radius squared — enter the inner diameter and the tool halves it.
- •Assuming volume scales with liquid depth. The fill input is the depth as a % of the inner diameter, and partial fill follows the circular-segment area — at 25% depth the pipe holds only about 19.6% of its full volume.
Frequently asked questions
How do I calculate the volume of a pipe?+
Volume = π × radius² × length, where the radius is half the inner diameter. A 4 inch ID pipe 100 ft long holds π × (2/12)² × 100 = 8.73 ft³ = 65.3 US gallons.
Is nominal pipe size the same as the inner diameter?+
No. Nominal pipe size (NPS) is a label, not the bore. A “4 inch” Schedule 40 steel pipe has a 4.026 in actual inner diameter, and Schedule 80 has 3.826 in because the wall is thicker. This calculator uses the actual bore from ASME B36.10M.
Does pipe schedule change the volume?+
Yes. A higher schedule means a thicker wall and a smaller inner diameter, so it holds less. At NPS 4, Schedule 80 holds roughly 10% less than Schedule 40 over the same length.
How do I calculate the volume of a partially full pipe?+
For a horizontal pipe, the filled cross-section is a circular segment, so the volume is not proportional to the liquid depth. Enter the fill depth as a percentage of the inner diameter and the calculator applies the circular-segment area before multiplying by length — at 25% depth a pipe holds about 19.6% of its full volume.
Methodology & sources
Volume is computed as π × radius² × length, carrying full precision and using exact π. The inner diameter is either entered directly or derived from nominal pipe size and schedule using outside diameter and wall thickness from ASME B36.10M (inner diameter = OD − 2 × wall).
Partial fill uses the circular-segment area of the filled cross-section. Gallon and litre conversions use the exact factors 1 ft³ = 7.480519 US gal = 28.3168 L.
- ASME B36.10M — Welded and Seamless Wrought Steel Pipe (dimensions) — verified June 28, 2026
Last reviewed June 28, 2026. Estimates are indicative — verify against current product specs and local requirements before ordering.
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