How Many Gallons in a Tank or Pipe? Round, Square and Horizontal
Part of the project planner: Planning pools, ponds and water storage.
A cylinder 4 ft across and 6 ft high holds 564 gallons, and 100 ft of 4 inch pipe holds 65.3 gallons. Both come from the same formula, π × radius² × length, with one cubic foot equal to 7.48 US gallons. The tank volume calculator and pipe volume calculator do your own sizes, and the charts below cover common ones.
Gallons in a round tank standing up
Capacity by diameter and height, in US gallons:
| Diameter | 4 ft high | 6 ft high | 8 ft high |
|---|---|---|---|
| 2 ft | 94 | 141 | 188 |
| 3 ft | 212 | 317 | 423 |
| 4 ft | 376 | 564 | 752 |
| 5 ft | 588 | 881 | 1,175 |
| 6 ft | 846 | 1,269 | 1,692 |
| 8 ft | 1,504 | 2,256 | 3,008 |
A tank on its side, part full
A horizontal cylinder is not linear: a small depth holds much less than the same share of the capacity. For a tank 4 ft across and 8 ft long (752 gallons when full):
| Depth of liquid, as a share of the diameter | Share of the capacity |
|---|---|
| 10% | 5.2% |
| 25% | 19.6% |
| 50% | 50.0% |
| 75% | 80.4% |
| 90% | 94.8% |
| 100% | 100.0% |
Measure the depth with a dip stick, and use the calculator to read the gallons.
Gallons in pipe
By inside diameter; the real inside diameter is smaller than the nominal size for most pipe:
| Inside diameter | Gallons per foot | Gallons per 100 ft | Liters per 100 ft |
|---|---|---|---|
| 0.5 in | 0.0102 | 1.02 | 3.9 |
| 0.75 in | 0.0229 | 2.29 | 8.7 |
| 1 in | 0.0408 | 4.08 | 15.4 |
| 1.5 in | 0.0918 | 9.18 | 34.7 |
| 2 in | 0.1632 | 16.32 | 61.8 |
| 3 in | 0.3672 | 36.72 | 139.0 |
| 4 in | 0.6528 | 65.28 | 247.1 |
| 6 in | 1.4688 | 146.88 | 555.9 |
| 8 in | 2.6112 | 261.12 | 988.3 |
Doubling the pipe diameter holds four times the water. Hot-water pipe loses heat while it holds cold water, so a long run wastes the volume above each time you open the tap.
The formulas
- Vertical cylinder: π × (diameter ÷ 2)² × height, in feet, × 7.48 for gallons.
- Horizontal cylinder: the area of the circular segment filled by the liquid × the length.
- Rectangular tank: length × width × height × 7.48.
- Pipe: π × (inside diameter in inches ÷ 24)² × length in feet × 7.48.
Use inside dimensions, and leave an air space at the top for expansion. For propane, stop at 80%. See also the cubic feet calculator. Estimates only.
Frequently asked questions
How many gallons are in a round tank?
π × radius² × height × 7.48. A tank 4 ft across and 6 ft high holds 564 gallons.
How do you calculate a horizontal tank that is part full?
The volume does not rise in step with the depth. A tank on its side filled to a quarter of its diameter holds 19.6% of its capacity, and to half its diameter, half. The calculator uses the real geometry.
How many gallons are in 100 feet of 4 inch pipe?
65.3 gallons (247 liters), which is 0.653 gallons per foot.
How many gallons are in a cubic foot?
About 7.48 US gallons. A cubic foot of water weighs about 62.4 pounds, and a gallon about 8.34 pounds.
How much does a full tank weigh?
A full 564 gallon tank holds about 4,704 pounds of water, plus the weight of the tank.
More guides
Tools & materials for this project
As an Amazon Associate we earn from qualifying purchases. These links do not change what you pay.
Estimates only. Quantities depend on your materials, site and supplier. Confirm important numbers before you order, and follow local building codes for anything structural.