Pool Volume Calculator
Calculate exactly how many gallons or liters your swimming pool holds based on its shape, size, and average depth — for accurate chemical dosing and water cost estimates.
For a flat-bottom pool, enter the same depth in both fields.
Cost to fill (water rate per gallon)
Calculate water cost
Total Volume
21,065
gallons
Surface Area
512
sq ft
Cubic Volume
2,816
cubic ft
Fill Cost
$84
to fill
Main Pool
Avg depth 5.5 ft · 512 sq ft
21,065
gallons
What is a Pool Volume Calculator?
A pool volume calculator is a tool that determines exactly how much water your swimming pool holds, measured in gallons or liters. It uses your pool's shape, dimensions, and average depth to compute the volume, removing the guesswork that leads to incorrectly balanced water and wasted chemicals.
Knowing your pool's volume is the single most important number in pool maintenance. Nearly every chemical — chlorine, pH increaser and decreaser, alkalinity adjuster, algaecide, and shock — is dosed based on how many gallons of water you have. Get the volume wrong and you either waste money over-treating or leave your pool unsafe and cloudy by under-treating.
This calculator supports rectangular, round, and oval pools, accounts for the difference between the shallow and deep ends through average depth, and even estimates the cost to fill your pool based on your local water rate. Whether you have an above-ground pool or a custom in-ground design, you get an accurate volume in seconds.
How to Use the Pool Volume Calculator
Select Pool Shape
Choose rectangular, round, or oval to match your pool. The calculator adjusts the area formula automatically.
Enter Dimensions
Provide length and width (or diameter for round pools). Switch to metric units if you measure in meters.
Set Shallow & Deep Depth
Enter both depths so the calculator can find your true average depth. Use the same value twice for a flat-bottom pool.
Review Volume & Cost
See total gallons, surface area, cubic volume, and the estimated cost to fill, with charts comparing each pool.
The Pool Volume Formula Explained
Pool volume is calculated in three steps — find the surface area, multiply by average depth, then convert to gallons:
1. Average Depth
Average Depth = (Shallow Depth + Deep Depth) ÷ 2
2. Surface Area (by shape)
Rectangle = Length × Width
Round = π × (Diameter ÷ 2)²
Oval = π × (Length ÷ 2) × (Width ÷ 2)
3. Volume in Gallons
Gallons = Surface Area × Average Depth × 7.48
For metric, cubic meters × 1,000 = liters.
Worked example: A 32 ft × 16 ft rectangular pool with a 3 ft shallow end and 8 ft deep end has an average depth of 5.5 ft. Surface area is 512 sq ft, so volume = 512 × 5.5 × 7.48 = ~21,063 gallons.
Example Calculations
Tips for Measuring Pool Volume
Measure at the water line
Take length and width measurements at the actual water surface, not the deck edge, for the most accurate area.
Average several depth readings
For irregular or sloped bottoms, take depth readings at multiple points and average them for a better estimate.
Round pools use diameter
Measure straight across the widest point through the center to get the true diameter, then the calculator handles the rest.
Account for the deep end slope
Most pools transition gradually. Using shallow + deep ÷ 2 captures this far better than a single depth number.
Re-check after a refill
If you lower the water level for winter or repairs, your effective volume changes — recalculate before dosing chemicals.
Keep your number handy
Write your final gallon figure on the equipment pad or in your pool app so chemical dosing is always quick and accurate.
Why Pool Volume Drives Everything in Pool Care
Pool chemistry is all about concentration — parts per million (ppm) of chlorine, the right pH, and balanced alkalinity. Concentration depends entirely on the total volume of water. When you add a pound of shock to 10,000 gallons, you get double the concentration you would in 20,000 gallons. That is why an accurate volume is the foundation of a safe, clear pool.
Volume also determines how you size your equipment. Pumps and filters are rated by turnover — the ability to circulate your entire water volume within a target window, usually 8 to 10 hours. Heaters are sized by the BTUs needed to raise a given number of gallons by a certain temperature. Under-size either one and your pool will struggle to stay clean and comfortable.
| Pool Type | Typical Size | Approx. Volume |
|---|---|---|
| Small above-ground | 15 ft round, 4 ft deep | ~5,000 gallons |
| Medium above-ground | 24 ft round, 4.5 ft deep | ~15,000 gallons |
| Average in-ground | 32 × 16 ft, 5.5 ft avg | ~21,000 gallons |
| Large in-ground | 40 × 20 ft, 6 ft avg | ~36,000 gallons |
For water balancing standards and detailed chemistry guidance, see the CDC's Healthy Swimming resources and the Pool Safely program from the U.S. CPSC for safe pool operation.
Frequently Asked Questions
How do I calculate the volume of my pool?
Multiply the pool's surface area by its average depth to get cubic feet, then multiply by 7.48 to convert to gallons. Average depth is the shallow end depth plus the deep end depth divided by two. For a round pool, surface area is π × radius². This calculator handles all of these conversions automatically.
How many gallons is my swimming pool?
A typical 32 ft × 16 ft rectangular pool with an average depth of 5.5 ft holds roughly 21,000 gallons. Volume depends heavily on shape and depth, so enter your exact dimensions for an accurate figure. The calculator supports rectangular, round, and oval pools.
What is average depth and why does it matter?
Average depth accounts for pools that have both a shallow and deep end. Add the shallow depth to the deep depth and divide by two. Using only one depth would significantly over- or under-estimate your volume, which throws off chemical dosing.
Why do I need to know my pool volume?
Knowing your exact volume is essential for correctly dosing chlorine, pH adjusters, algaecide, and other chemicals. It also helps you size pumps, heaters, and filters, and estimate water and heating costs accurately.
How do I convert cubic feet to gallons?
Multiply cubic feet by 7.48 to get US gallons. For metric calculations, one cubic meter equals 1,000 liters. The calculator does this conversion for you based on the unit system you select.
Does pool shape change the formula?
Yes. Rectangular pools use length × width for surface area, round pools use π × radius², and oval pools use π × (length/2) × (width/2). After finding surface area, all shapes multiply by average depth and convert to gallons or liters the same way.