Stock Tank Pool Calculator
This stock tank pool calculator finds the gallons a round tank holds from its diameter and depth: an 8 ft tank filled 2 ft deep holds about 752 gallons.
Stock tank pool calculator: gallons in a round tank
A stock tank pool calculator turns the diameter and water depth of a round tank into gallons. A stock tank is a galvanized or plastic livestock trough that people fill as a small plunge pool. The tank is a cylinder, so the volume is the area of the circle times the depth.
Gallons = pi × (diameter in inches ÷ 24)² × depth in feet × 7.48.
In this tool, the first field is the water depth in feet and the second is the diameter in inches. The cost box multiplies gallons by your water price per gallon, which starts at one cent.
Worked examples
Example 1, the default tank. 96 in (8 ft) diameter, 2 ft of water.
- Radius: 96 ÷ 24 = 4 ft
- Cubic feet: 3.1416 × 16 × 2 = 100.53
- Gallons: 100.53 × 7.48 = 751.97
- Water cost at $0.01 per gallon: $7.52
Example 2, a smaller tank. 72 in (6 ft) diameter, 2 ft of water.
- Cubic feet: 3.1416 × 9 × 2 = 56.55
- Gallons: 422.98
Example 3, the 8 ft tank filled less. 1.5 ft of water.
- Cubic feet: 75.40
- Gallons: 563.98
Gallons by tank size and depth
| Diameter | Water depth | Gallons |
|---|---|---|
| 6 ft (72 in) | 1.5 ft | 317.24 |
| 6 ft (72 in) | 2 ft | 422.98 |
| 7 ft (84 in) | 2 ft | 575.73 |
| 8 ft (96 in) | 1.5 ft | 563.98 |
| 8 ft (96 in) | 1.75 ft | 657.98 |
| 8 ft (96 in) | 2 ft | 751.97 |
A foot of extra diameter adds more water than a few inches of depth does, because the area grows with the square.
Weight of the water
Water weighs about 8.34 lb per gallon. The default 8 ft tank holds 751.97 gallons, which is 751.97 × 8.34 = about 6,271 lb, or a little over 3 tons, before you add the tank and the people. Set the tank on level, firm ground. Soft or sloping ground can shift, and a full tank is not something you want to move.
Measuring the tank
Use the inside diameter at the water line. Measure across the tank through the center with a tape. For the depth, mark where the water will sit with a stick or a ruler, and measure from the floor to that mark. Stock tanks often have a slightly sloped bottom or ribs, so take a few readings and average them.
Keeping the water clean
Without treatment, a tank turns green in warm weather. Options include a pump and filter, regular chemical dosing, or draining and refilling often. For chemicals, follow the product label, and use the gallons figure from this page to read the dose. The pool chlorine calculator helps you think about the amount, though the label has the final say.
Safety rules to check
- Many places treat a container of water deeper than a set depth as a pool that needs a barrier or a cover. Ask your local building office.
- Any pump or heater near water must have ground-fault protection. Have a licensed electrician install it.
- Never leave children alone near an open tank.
- Keep a cover on when not in use.
Common mistakes
- Entering the tank height instead of the water depth.
- Typing the diameter in feet. This field wants inches.
- Using the outside diameter of the tank.
- Forgetting the weight when choosing a spot.
Filling and draining
A hose fills a tank slowly. If your hose delivers 5 gallons per minute, the 8 ft tank at 751.97 gallons takes about 751.97 ÷ 5 = 150 minutes, or two and a half hours. Measure your own flow by timing how long a 5 gallon bucket takes to fill. Draining a tank is best done onto a lawn or garden bed that can absorb the water, and not toward a neighbor or a storm drain, unless local rules allow it. Treated water may have limits on where it can go.
Related calculators
For other round shapes, use the round pool calculator. The hot tub volume calculator covers rectangular spas, and the pool gallons calculator handles larger pools.
Frequently asked questions
How many gallons does a stock tank pool hold?
It depends on the diameter and the water depth. Gallons = pi × radius² × depth × 7.48, with feet for the radius and depth. An 8 ft tank (96 in) filled 2 ft deep holds 751.97 gallons. A 6 ft tank at the same depth holds 422.98.
Why are stock tank pools so popular?
They cost less than a built pool, go up in an afternoon, and fit in a small yard. They are also easy to move or drain. Some owners add a pump and filter, and some treat the water with chemicals like a pool.
What size pump and filter do I need for a stock tank pool?
Use the gallons to find the flow. For example, 752 gallons in 8 hours is 752 ÷ 480 = 1.57 GPM, so a small pump is enough for circulation. Check the filter's rating and follow the product label for chemicals.
Do I fill a stock tank pool to the very top?
Usually not. The water sits several inches below the rim so it does not spill over when people get in. Measure the actual water depth, not the tank height, and enter that.
Does the diameter measurement mean inside or outside the tank wall?
Use the inside diameter at the water line, since that is the water's width. The outside is a little larger because of the wall. For a tank labeled 8 ft, the inside is a bit under that, so your result will run slightly high.
Estimates only. Verify quantities with your supplier before purchasing.