# Pool Gallon Calculator

Pool gallon calculator for rectangle, round, oval, and kidney pools. Pool gallon calculator oval and pool gallon calculator rectangle both supported, plus kidney shapes.

## What this calculates

Find out exactly how many gallons of water your swimming pool holds. This pool gallon calculator handles rectangle, round, oval, and kidney shapes, plus pools with a sloped bottom (shallow end plus deep end). Knowing gallons is step one for every chemical dose, pump sizing decision, and heater sizing decision you make about your pool.

## Inputs

- **Pool Shape** — options: Rectangle, Round / Circular, Oval, Kidney / Freeform — Rectangle, round, oval, or kidney. Works for in-ground and above-ground pools.
- **Length (or Diameter)** (ft) — min 1, max 300 — Longest dimension. For round pools, enter the diameter.
- **Width** (ft) — min 0, max 200 — Ignored for round pools.
- **Depth Input** — options: Single average depth, Shallow end + deep end — Choose sloped for pools with a deep end.
- **Average Depth** (ft) — min 0, max 30 — Used when depth input = single average depth.
- **Shallow End Depth** (ft) — min 0, max 15 — Used when depth input = shallow + deep.
- **Deep End Depth** (ft) — min 0, max 30 — Used when depth input = shallow + deep.

## Outputs

- **Pool Volume** — Total water capacity in US gallons
- **Pool Volume (metric)**
- **Volume (cubic feet)**
- **Surface Area**
- **Average Depth Used**

## Details

Pool Gallon Formulas by Shape

  - Pool gallon calculator rectangle: Length x Width x Avg Depth x 7.48 gal/ft^3

  - Round pool: pi x Radius^2 x Avg Depth x 7.48

  - Pool gallon calculator oval: pi x (Length/2) x (Width/2) x Avg Depth x 7.48

  - Pool gallon calculator kidney: Length x Width x Avg Depth x 7.0 (irregular bottom coefficient)

For sloped pools, average depth equals (shallow + deep) / 2. This works for most residential in-ground pools where the floor slopes evenly from a shallow end to a deep end.

Typical Pool Sizes in Gallons

  - 18 ft round above-ground (52 in deep): about 8,600 gallons

  - 24 ft round above-ground (52 in deep): about 14,650 gallons

  - 12 x 24 ft oval above-ground: about 8,000 gallons

  - 16 x 32 ft rectangular in-ground (5 ft avg): about 19,150 gallons

  - 20 x 40 ft rectangular in-ground (3-8 ft slope): about 33,000 gallons

  - Kidney 16 x 32 ft at 5 ft avg depth: about 17,900 gallons

Why Pool Gallons Matter

Every chemical dose scales with pool volume. Chlorine, pH adjusters, cyanuric acid, algaecide, and salt all key off gallons. Filter capacity, pump horsepower, and heater BTU output are also sized against gallons. A 10% error in pool volume means a 10% error in every chemical dose and a 10% error on every equipment size. Ten minutes with a tape measure and this calculator is cheaper than a season of cloudy water.

Pool Gallon Calculator Oval Tips

Oval above-ground pools are measured by the overall length (longest point) and the overall width (widest point). The formula uses pi x (Length/2) x (Width/2) for surface area, which is the area of an ellipse. A typical 12 x 24 ft oval at 4 ft average depth is pi x 6 x 12 x 4 x 7.48 = about 6,770 gallons. Most oval liner pools have a flat bottom so single average depth is the right choice.

Pool Gallon Calculator Kidney Shape Notes

Kidney-shaped and freeform pools have curved perimeters and irregular bottoms that make simple length x width math inaccurate. Pool industry practice is to multiply length x width x 0.85 for surface area and use a 7.0 gal/ft^3 coefficient instead of the textbook 7.48, which together account for the curvature and the uneven bottom. Expect results within 5-10% of the real volume. For precision, measure the pool in sections (main body + spa + sun shelf) and add the volumes.

## Frequently Asked Questions

**Q: How do I use the pool gallon calculator rectangle option?**

A: Pick Rectangle from the shape dropdown, enter length and width in feet, then choose either a single average depth or a shallow/deep split. A 16 x 32 ft rectangle pool with 5 ft average depth calculates as 16 x 32 x 5 x 7.48 = about 19,150 gallons. The calculator rounds to the nearest gallon.

**Q: Does the pool gallon calculator oval work for above-ground pools?**

A: Yes. The pool gallon calculator oval setting uses the ellipse formula pi x (Length/2) x (Width/2), which matches how Intex, Bestway, and other above-ground oval pools are measured. A 15 x 30 ft oval at 4.3 ft deep is pi x 7.5 x 15 x 4.3 x 7.48 = about 11,380 gallons.

**Q: How accurate is the pool gallon calculator kidney shape?**

A: Kidney and freeform pools use a length x width x 0.85 surface area approximation with a 7.0 gal/ft^3 coefficient. That lands within 5-10% of actual volume for most residential kidney shapes. For exact numbers on true freeform pools, measure the main body and spa separately and add them.

**Q: Should I use the inside water measurement or the outside edge?**

A: Always use inside water measurements. For vinyl liner pools, measure between the liner walls at the water line. For concrete or plaster pools, measure waterline to waterline. Don't include the coping, deck, or skirt; that padding overstates the pool volume by 10-20% and throws off every chemical dose downstream.

**Q: What about pools with a deep end and a shallow end?**

A: Switch Depth Input to Shallow end + deep end. The calculator averages them: (3 ft + 8 ft) / 2 = 5.5 ft average depth. A 16 x 32 ft rectangle with a 3 to 8 ft slope comes out to about 21,100 gallons. This assumes a roughly linear slope between the two ends, which is how most residential pools are built.

**Q: How many gallons is a typical 24 ft round above-ground pool?**

A: A 24 ft round above-ground pool at 52 in (4.33 ft) deep holds about 14,650 gallons: pi x 12^2 x 4.33 x 7.48. Common 18 ft rounds hold about 8,600 gallons and 15 ft rounds about 5,300 gallons. The manufacturer sticker usually lists a number, but measure yours to confirm because liner wear and sand leveling affect actual depth.

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Source: https://vastcalc.com/calculators/everyday/pool-gallon
Category: Everyday Life
Last updated: 2026-04-08