Pool Volume Calculator
Knowing your pool's exact gallons is the foundation of every other pool chemistry decision. Salt levels, chlorine doses, shock treatments, and pump run times are all calculated based on this one number. A swimming pool volume calculator removes the guesswork from finding it. Get the volume wrong, and every chemical calculation after it will be off too.
Use the Calculator Below
Use our pool volume calculator to find your exact gallons based on your pool's shape, length, width, and average depth. Select your pool shape, enter your measurements in feet, and the calculator instantly returns your total volume in gallons.
Quick Answer
A pool volume calculator finds your pool's total water capacity in gallons based on shape, length, width, and average depth. For a standard rectangular pool: length x width x average depth x 7.48. A 32 x 16-foot pool with a 5-foot average depth holds roughly 19,148 gallons. Round, oval, and kidney-shaped pools use adjusted versions of this formula.
Introduction
Knowing your pool's exact gallons is the foundation of every other pool chemistry decision. Salt levels, chlorine doses, shock treatments, and pump run times are all calculated based on this one number. A swimming pool volume calculator removes the guesswork from finding it. Get the volume wrong, and every chemical calculation after it will be off too.
Most pool owners do not know their exact gallons. They guess, or rely on a builder's estimate from years ago that may no longer be accurate if the pool has been resurfaced or modified. A tool like this one solves that in seconds using your pool's actual measurements.
The Formula Behind This Tool
This pool water volume calculator runs on simple geometry: surface area multiplied by average depth, converted to gallons.
Rectangular Pools
This is the most common formula, since most in-ground and above-ground pools are rectangular or close to it.
Round Pools
Square the radius (half the diameter), multiply by pi (approximately 3.14159), then by depth and the gallon conversion factor.
Oval and Kidney-Shaped Pools
Oval and kidney pools use a similar formula with an adjustment factor (commonly 0.45 to 0.585) to account for the curved shape, since a true oval or kidney holds less water than a rectangle of the same outer dimensions.
Why 7.48?
One cubic foot of water holds 7.48 gallons. Every volume formula above calculates cubic feet first, then converts to gallons using this constant.
Finding Your Average Depth
Most pools are not a uniform depth from end to end. To get an accurate average:
For example, a pool with a 3-foot shallow end and an 8-foot deep end has an average depth of 5.5 feet.
If your pool has a long flat section before sloping down, splitting it into two sections and calculating each separately gives a more accurate result than a simple average.
- Measure the shallow end depth separately.
- Measure the deepest point separately.
- Calculate the average depth before using the calculator.
- Re-measure after resurfacing or major pool modifications.
Practical Example: 18,000-Gallon Target Pool
Suppose you are checking a rectangular pool that is 30 feet long and 15 feet wide, with a shallow end of 3 feet and a deep end of 8 feet.
Find average depth
(3 + 8) / 2 = 5.5 feet
Multiply length by width
30 x 15 = 450 square feet
Multiply by average depth
450 x 5.5 = 2,475 cubic feet
Convert to gallons
2,475 x 7.48 = approximately 18,521 gallons
Calculation Summary
The calculator automatically performs every step of the calculation after you enter your pool measurements.
Measure Your Pool
Length, width, shallow end depth and deep end depth.
Calculate Average Depth
The calculator uses the average depth for accurate volume estimation.
Choose Pool Shape
Rectangular, round, oval or kidney-shaped.
Instant Gallons Result
The final result is displayed instantly without manual calculations.
Common Pool Size Examples
| Pool Shape | Dimensions | Average Depth | Volume (Gallons) |
|---|---|---|---|
| Rectangular | 20 ft × 10 ft | 5 ft | ~7,480 |
| Rectangular | 30 ft × 15 ft | 5.5 ft | ~18,521 |
| Rectangular | 32 ft × 16 ft | 5.5 ft | ~21,113 |
| Round | 24 ft diameter | 4.5 ft | ~15,222 |
| Oval | 18 ft × 33 ft | 4 ft | ~14,500 |
How to Measure Your Pool for Volume
Knowing how to calculate pool volume yourself starts with three measurements:
Measure Length & Width
Measure length and width at the widest points, in feet.
Measure Pool Depth
Measure depth at the shallow end and the deep end separately.
Calculate Average Depth
Calculate average depth by adding both depths and dividing by two.
Select Pool Shape
Select your pool shape in the calculator (rectangular, round, oval, or kidney).
Enter Measurements
Enter all measurements into the calculator.
Review Your Result
Review your result and round features (ledges, steps, spas) separately if present.
Save Your Gallons Number
Save your gallons number. You will need it for every chemical calculator going forward.
Important Note
Always re-measure if you have resurfaced, modified, or added features to your pool, since these changes affect total volume.
Common Mistakes to Avoid
Using builder estimates instead of real measurements.
Construction plans round numbers and do not account for slope changes over time.
Measuring only the deep end depth.
Using the deepest point instead of the average overstates volume significantly.
Ignoring pool features.
Tanning ledges, built-in spas, and steps add or subtract volume a basic formula misses.
Mixing units.
Measure consistently in feet, since mixing feet and inches throws off every result.
Forgetting to recalculate after changes.
A new shallow end, added spa, or resurfacing job changes your gallons.
Confusing surface area with volume.
Square footage alone tells you nothing about how much water the pool holds.
Measurement Tip
Accurate measurements produce accurate gallon estimates. Every chemical calculator on your pool depends on this one number, so take your measurements carefully before calculating.