Quick Answer

A 30 × 15 ft rectangular pool with 5 ft average depth holds approximately 16,831 gallons. A 24 ft round pool at 4 ft deep holds approximately 13,536 gallons.

Pool Shape Rectangular Circular Oval

Length (ft)

Width (ft)

Shallow End (ft)

Deep End (ft)

Common Examples

Input	Result
Rectangular 30 × 15 ft, 3 ft shallow, 7 ft deep	Approximately 16,831 gallons (2,250 cu ft)
Circular 24 ft diameter, 4 ft constant depth	Approximately 13,536 gallons (1,810 cu ft)
Oval 30 × 15 ft, 5 ft average depth	Approximately 13,218 gallons (1,767 cu ft)
Rectangular 16 × 32 ft, 3.5 ft shallow, 7.5 ft deep	Approximately 21,064 gallons (2,816 cu ft)
Circular 18 ft diameter, 4 ft depth	Approximately 7,634 gallons (1,018 cu ft)

How It Works

The formulas

Rectangular pool:

V = Length (ft) × Width (ft) × Average Depth (ft)

This is the most straightforward case. Multiply the three dimensions together to get cubic feet.

Circular pool:

V = π × r² × Average Depth (ft)

Where r is the radius (half the diameter). A 24-foot diameter pool has a 12-foot radius. Multiply pi by the radius squared and then by the average depth.

Oval pool:

V = π × (Long Axis / 2) × (Short Axis / 2) × Average Depth (ft)

An oval pool is treated as an ellipse. The formula uses half the long axis and half the short axis in place of the radius squared from the circular formula.

Average depth

Most pools slope from a shallow end to a deep end. Average depth is calculated as:

Average Depth = (Shallow End + Deep End) / 2

For a pool with a 3-foot shallow end and a 7-foot deep end, the average depth is (3 + 7) / 2 = 5 feet. Using the true average rather than the deep end alone gives a significantly more accurate volume estimate.

Unit conversions

• 1 cubic foot = 7.48052 US gallons
• 1 cubic foot = 28.3168 liters

These factors convert the cubic foot result into the units most useful for chemical treatment and water delivery estimates.

Worked example

A rectangular pool measures 32 feet long by 16 feet wide. The shallow end is 3.5 feet and the deep end is 7.5 feet.

Average depth = (3.5 + 7.5) / 2 = 5.5 feet.

Volume = 32 × 16 × 5.5 = 2,816 cubic feet.

In gallons: 2,816 × 7.48052 = approximately 21,064 US gallons.

In liters: 2,816 × 28.3168 = approximately 79,740 liters.

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Frequently Asked Questions

How do I measure average depth?

For a pool that slopes uniformly from the shallow end to the deep end, average depth is (shallow end depth + deep end depth) / 2. Measure each depth at the point where the floor levels off at its shallowest and deepest. For pools with a flat bottom at the deep end and a slope transitioning to the shallow end, the same formula gives a close approximation.

How many gallons does a typical pool hold?

Most residential swimming pools hold between 10,000 and 30,000 gallons depending on size and depth. A small above-ground round pool (15 ft diameter, 4 ft deep) holds roughly 5,300 gallons. A standard in-ground pool (30 × 15 ft, 5 ft average depth) holds approximately 16,800 gallons. Large in-ground pools with deep ends can exceed 25,000 gallons.

Why do I need to know pool volume?

Pool volume is the foundation for three key calculations. First, chemical dosing: chlorine, shock, algaecide, and pH adjusters all have dosage rates specified per 1,000 gallons. Second, heater sizing: pool heaters are rated in BTUs and the volume determines how long heating takes and what size unit you need. Third, pump sizing: turnover rate (the time to circulate the full volume once) determines the required pump flow rate, typically 6 to 8 hours for a full turnover.

How do I calculate volume for an irregularly shaped pool?

For kidney-shaped, L-shaped, or freeform pools, divide the pool into simpler sections (rectangles or approximate ovals), calculate the volume of each section separately, and add the results. For a kidney shape, two overlapping circles or rectangles approximated to the widest and narrowest points is usually accurate enough for chemical dosing purposes. The error is typically within 5 to 10 percent.

How long does it take to fill a pool?

A standard garden hose delivers roughly 9 gallons per minute (GPM). At that rate, filling a 20,000-gallon pool takes approximately 20,000 / 9 = 2,222 minutes, or about 37 hours. A 5/8-inch hose at normal residential water pressure typically flows 9 to 17 GPM depending on pressure. Divide your pool's gallon volume by your hose's GPM to estimate fill time in minutes.

Learn More

How to Calculate Pool Volume

Learn how to calculate swimming pool volume in gallons for rectangular, round, and irregular pools. Includes formulas, worked examples, and a cubic feet to gallons conversion.