Calculate exact fluid capacity in US liquid gallons, Imperial gallons, linear gal/ft holding ratios, and total water weight.
Calculations are based on cylindrical formula \(V = \pi r^2 L\). Verify dimensions against manufacturer specs for code submittals.
The Pipe Volume Calculator in Gallons calculates the exact liquid volume in US liquid gallons and Imperial gallons for any cylindrical pipe, conduit, or tube run.
Working with metric units? Switch to our dedicated Pipe Volume Calculator in Litres or use the multi-material Pipe Volume Calculator.
Follow these 4 simple steps to calculate gallons in any pipe:
The gallon capacity of any cylindrical pipe is calculated by determining the internal volume in cubic inches and dividing by 231 (1 standard US gallon = 231 in³):
Gallons (US) = (π × r² × L) / 231 = (π × (ID / 2)² × (Length_ft × 12)) / 231 Where the variables represent:
| Nominal Size | Actual ID (Sch 40) | Gallons / Linear Ft | Gallons / 100 Ft | Filled Water Weight / 100 ft |
|---|---|---|---|---|
| 3/4" Pipe | 0.824 in | 0.0277 gal/ft | 2.77 gal | 23.1 lbs |
| 1" Pipe | 1.049 in | 0.0449 gal/ft | 4.49 gal | 37.4 lbs |
| 1-1/2" Pipe | 1.610 in | 0.1058 gal/ft | 10.58 gal | 88.2 lbs |
| 2" Pipe | 2.067 in | 0.1743 gal/ft | 17.43 gal | 145.4 lbs |
| 3" Pipe | 3.068 in | 0.3840 gal/ft | 38.40 gal | 320.3 lbs |
| 4" Pipe | 4.026 in | 0.6613 gal/ft | 66.13 gal | 551.5 lbs |
A contractor is installing 100 feet of 3-inch Schedule 40 PVC pipe (actual ID = 3.068 inches) and needs to verify total gallon capacity and water weight for support hangers.
Step-by-Step Math:
r = 3.068 / 2 = 1.534 inches100 ft × 12 = 1,200 inchesV = 3.14159 × (1.534)² × 1,200 = 8,870.47 in³8,870.47 / 231 = 38.399 US Gallons (31.97 Imperial Gallons)38.40 gal × 8.34 lbs/gal = 320.26 lbsA standard 2-inch Schedule 40 pipe (actual inside diameter = 2.067 inches) holds approximately 0.1743 US gallons per linear foot (1.74 gallons per 10 feet, 17.43 gallons per 100 feet). A theoretical true 2.000" ID pipe holds 0.1632 gallons per foot.
Divide the total internal volume in cubic inches by 231, because exactly 231 cubic inches equal 1 standard US liquid gallon: Gallons = Volume (in³) / 231.
1 US liquid gallon equals 231 cubic inches (approx. 3.7854 Litres), while 1 Imperial gallon equals 277.42 cubic inches (approx. 4.5461 Litres). 1 Imperial gallon is approximately 20% larger than a US gallon.
One US gallon of fresh water weighs approximately 8.34 pounds (3.785 kg) at standard room temperature (62°F / 16.7°C). One Imperial gallon of water weighs exactly 10.00 pounds (4.536 kg).
A 4-inch Schedule 40 pipe (ID = 4.026 inches) has a linear volume ratio of 0.6613 gallons per foot. Over a 50-foot run, the total fluid capacity is: 50 ft × 0.6613 gal/ft = 33.07 US gallons (approx. 275.8 lbs of water).
Heavier wall pipes (such as Schedule 80 PVC or Copper Type K) have smaller internal diameters than thinner wall pipes (Schedule 40 or Copper Type M) of the same nominal size, reducing the total gallon capacity.