How to Calculate Your Pool’s Water Volume Like a Pro

Ever wondered exactly how much water your pool holds? Whether you're adding chemicals, upgrading equipment, or just curious, knowing your pool’s volume is essential. Use our simple calculator or follow this guide to measure it yourself.

Get an Accurate Measurement

To get the right pool volume, always measure the actual water depth—not just the wall height. Most pools aren’t filled to the brim, so measuring from the top of the waterline ensures accuracy.

For irregularly shaped pools, you might need extra calculations. We’ll walk you through those at the end.

Quick Pool Volume Reference Chart

If your pool is a standard size, use the chart below for a quick estimate. Keep in mind that measuring your pool personally will always yield the most precise results.

Above Ground - 48” Wall Height Pool Size Gallons 15’ Round 5,300 18’ Round 7,600 20’ Round 9,400 24’ Round 13,600 27’ Round 17,200 28’ Round 18,500 11x25 Oval 6,500 15x25 Oval 7,800 15x30 Oval 8,900 18x33 Oval 10,600 18x38 Oval 14,000

Above Ground - 52” Wall Height Pool Size Gallons 15’ Round 5,800 18’ Round 8,300 20’ Round 10,200 24’ Round 15,300 27’ Round 18,600 28’ Round 20,000 11x25 Oval 7,000 15x25 Oval 8,400 15x30 Oval 9,600 18x33 Oval 11,500 18x38 Oval 15,200

InGround - Average Depth Pool Size Gallons 12x24 Rectangular 10,800 16x32 Rectangular 19,200 16x36 Rectangular 21,600 18x36 Rectangular 24,300 20x40 Rectangular 30,000 16x32 Oval 17,200 18x36 Oval 21,700 20x40 Oval 26,800 17x33 Grecian 19,700 17x37 Grecian 22,200 20x36 Grecian 24,300 20x44 Grecian 30,300 16x30 Kidney 14,900 16x34 Kidney 16,500 20x38 Kidney 20,200

Step-by-Step Pool Volume Calculation

The Basics of Pool Volume Calculation

To determine your pool’s total volume, you’ll first need to calculate the surface area and average depth. Here’s what you need:

Length (L)

Width (W)

Depth (D) or Height (H)

Diameter (d) (for circular pools)

Radius (r) (for circular pools)

Pi (3.14)

For rectangular pools, multiply the length and width for surface area, then incorporate the depth for volume. One cubic foot of water equals 7.5 gallons, so you’ll multiply your cubic foot measurement by 7.5 to get the total volume in gallons.

Pool Volume Calculations by Shape

Rectangular Pool Volume

Your formula will vary based on whether your pool has a consistent depth or multiple depth levels.

✔ Single Depth Pool

Formula: L × W × D × 7.5 = V (gallons)

Example: A 32 ft. x 16 ft. pool with a depth of 4 ft.

32 × 16 × 4 × 7.5 = 15,360 gallons

✔ Sloped Pool (Shallow to Deep End)

First, calculate the average depth: (Shallow Depth + Deep Depth) ÷ 2

Example: If your pool is 3 ft. at the shallow end and 9 ft. at the deep end:

(3 + 9) ÷ 2 = 6 ft. average depth

32 × 16 × 6 × 7.5 = 23,040 gallons

✔ Pool with a Sharp Drop-Off

Treat the shallow and deep sections as separate pools.

Calculate each section’s volume using the constant depth formula, then add the two volumes together for the total pool volume.

Round Pool Volume

For circular pools, use this formula:

Formula: 3.14 × r² × D × 7.5 = V (gallons)

Example: A pool with an 18 ft. diameter (9 ft. radius) and 4 ft. depth:

3.14 × (9 × 9) × 4 × 7.5 = 7,630 gallons

Irregular-Shaped Pool Volume

For pools with non-traditional shapes (like kidney or oval pools), break them down into smaller, simpler shapes (like rectangles or circles). Calculate the volume of each section separately using the appropriate formulas, then sum them to get the total volume.

When to Call a Pool Professional

If your pool shape makes calculations tricky or you want a highly precise measurement, consider hiring a pool expert. Accurate volume measurements are crucial not only for chemical balancing but also for installing new pumps, filters, or heaters.

Keep Your Pool Volume Handy

Knowing your pool’s volume helps you maintain proper chemical levels and keeps your water clean and safe. Keep your final calculations on hand—you’ll refer to them often as a pool owner!