Oval Pool Water Volume Calculator

This calculator works out the water volume of an oval swimming pool in US gallons and litres. You enter the pool’s length, width, and either the average depth or the deep and shallow end depths, and it returns the total volume. The calculation uses the standard formula for an oval pool, which treats it as a rectangle with rounded ends.

Formula

The volume of an oval pool is approximated by the formula:

V = L × W × D × 0.9

Where:

• V = volume in cubic feet
• L = length of the pool in feet
• W = width of the pool in feet
• D = average depth in feet, calculated as (deep end depth + shallow end depth) / 2
• 0.9 = a shape factor that accounts for the rounded ends of an oval pool

To convert cubic feet to US gallons, multiply by 7.48052. To convert to litres, multiply by 28.3168.

Worked Example

Using the default values from the calculator (length = 24 ft, width = 12 ft, deep end = 6 ft, shallow end = 3 ft):

1. Average depth = (6 + 3) / 2 = 4.5 ft
2. Volume in cubic feet = 24 × 12 × 4.5 × 0.9 = 1166.4 ft³
3. US gallons = 1166.4 × 7.48052 ≈ 8726 gallons
4. Litres = 1166.4 × 28.3168 ≈ 33028 litres

The calculator rounds the gallons to 8726 and the litres to 33028.

Why the 0.9 Shape Factor?

An oval pool is not a perfect rectangle. The ends are curved, so the actual surface area is less than length × width. The factor 0.9 is a widely used approximation for typical above-ground oval pools. It works well for most residential pools, but the exact factor can vary slightly (from about 0.85 to 0.95) depending on how rounded the ends are. For a pool with very tight curves, the factor is closer to 1.0; for a highly elongated oval, it is closer to 0.85. If you need extreme precision, measure the pool’s surface area by other means, but for practical purposes 0.9 is accurate enough.

How to Measure Your Pool Correctly

To get an accurate volume, you need accurate measurements:

• Length: measure from the outside edge of one end to the outside edge of the other, at the widest point of the oval.
• Width: measure across the pool at its widest point, perpendicular to the length.
• Depth: measure the water depth, not the pool wall height. For an above-ground pool, water depth is usually a few inches below the top. For an in-ground pool, measure the actual water depth at the deep and shallow ends.

If your pool has a constant depth, enter the same value for both deep and shallow ends.

Common Mistakes and How to Avoid Them

• Using wall height instead of water depth: This overestimates volume. Always measure the water level, not the pool’s structural height.
• Mixing units: If you measure in feet, the formula gives cubic feet. If you measure in metres, the formula gives cubic metres (1 m³ = 1000 L). Do not mix feet and metres.
• Forgetting the 0.9 factor: Without it, you overestimate by about 10%.
• Assuming a rectangular shape: Oval pools have less volume than a rectangle of the same length and width. The 0.9 factor corrects for this.

When to Use This Calculator

You need the water volume for several practical reasons:

• Chemical dosing: Most pool chemicals (chlorine, pH adjusters, algaecides) are dosed per 10,000 gallons or per litre. An accurate volume prevents under- or over-dosing.
• Filling time: Knowing the volume helps estimate how long it will take to fill the pool with a given hose flow rate.
• Heating costs: The volume determines how much energy is needed to raise the water temperature.
• Water bills: If you pay for water, you can estimate the cost of filling or topping up.

Limitations of the Formula

This formula assumes a symmetrical oval with a smooth bottom. Real pools may have sloped floors, steps, or irregular shapes. For an in-ground pool with a hopper bottom (steep drop-off), the average depth method is still a good approximation, but for a pool with a very complex shape, a more detailed calculation or a professional measurement is recommended. The formula also does not account for water displaced by steps, ladders, or other fixtures, which is usually negligible.

Frequently Asked Questions

How many gallons is a 24×12 oval pool?

With a constant depth of 4 feet, a 24×12 oval pool holds about 7,760 US gallons (29,380 litres). The exact volume depends on the actual water depth; use the calculator with your specific depths.

What is the difference between an oval and a kidney-shaped pool?

An oval is a symmetrical shape with two parallel sides and rounded ends. A kidney pool has one side that curves inward, giving it an irregular shape. The volume formula for a kidney pool is different and often uses a factor of 0.85 or a more complex geometric calculation.

Should I measure the pool when it’s full or empty?

Measure the water depth when the pool is full, because that is the actual volume you are dealing with. The pool’s structural dimensions (length and width) can be measured at any time, but the depth should be the water depth, not the wall height.

How do I convert gallons to litres?

Multiply the number of US gallons by 3.78541 to get litres. For example, 10,000 US gallons is 37,854 litres. Note that there are also Imperial gallons (used in the UK), which are larger; this calculator uses US gallons.

Why does my pool hold less water than the manufacturer says?

Manufacturers often list the pool’s capacity based on the maximum wall height and a perfectly flat bottom. In reality, the water level is usually a few inches below the top, and the bottom may not be perfectly flat, so the actual volume is slightly lower.

Can I use this for a round pool?

No. A round pool uses a different formula: V = π × (diameter/2)² × depth. This calculator is specifically for oval shapes. For a round pool, use a round pool volume calculator.

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in l | Pool Length | ft | 24 | 0
in w | Pool Width | ft | 12 | 0
in d_deep | Deep End Depth | ft | 6 | 0
in d_shallow | Shallow End Depth | ft | 3 | 0
out avg_depth | Average Depth | ft | (d_deep + d_shallow) / 2 | 2
out volume_ft | Volume (cubic feet) | ft³ | l * w * avg_depth * 0.9 | 0
out gallons | Water Volume | US gal | volume_ft * 7.48052 | 0
out litres | Water Volume | L | volume_ft * 28.3168 | 0