Calculator
Pool Volume Calculator
A pool's volume is not its surface area times its deepest point — that overstates a typical sloped-bottom pool by a wide margin, because most of the pool isn't as deep as the deep end. The number that actually belongs in a volume calculation is the average of the shallow and deep depths, applied evenly across the whole surface area, which approximates a sloped floor reasonably well without needing to model the exact slope.
This calculator works out surface area from the pool's actual shape — rectangular, round or oval, each with a different area formula — multiplies by average depth to get volume, and converts that to gallons for chemical dosing and litres for reference. It also works out the pump flow a given turnover time requires, because volume alone doesn't tell you what size pump and filter the pool actually needs.
Calculate your quantity
hours to circulate the whole volume once
Pool volume
17,236 gallons
- Surface area
- 512 sq ft
- Average depth
- 4.5 ft
- Volume
- 2,304 cu ft
- Volume in litres
- 65,243 litres
- Pump flow for turnover
- 35.9 gpm
- Perimeter
- 96 ft
- Average depth, not maximum depth, sets the volume. Using the deep end alone would overstate this pool by 33%.
Shopping summary
- • A pump and filter rated for at least 36 gpm at your system's head
This is an estimate — confirm structural work with a professional.
How this calculation works
Surface area depends entirely on shape: a rectangular pool is simply length times width, a round pool uses the classic circle-area formula from its diameter, and an oval pool is approximated as an ellipse from its length and width. Average depth is the mean of the shallow and deep measurements — a reasonable approximation for a pool with a sloped floor transitioning between the two, though it does assume the transition is roughly linear rather than stepped.
Volume in cubic feet converts to gallons using the standard cubic-feet-to-gallons factor, and from gallons to litres using the standard gallons-to-litres factor — both fixed unit conversions, not estimates. Pump flow for a target turnover time is simply the total gallons divided by the number of minutes in that turnover window, which is the flow rate a pump and filter combination needs to sustain to cycle the entire pool volume once within the chosen time.
- Average depth, not maximum depth, sets the volume — using the deep end alone significantly overstates a typical pool's actual water volume.
- Shape matters: a round pool of a given diameter holds noticeably less water than a square pool of the same outer dimension, because a circle's area is smaller than the square that circumscribes it.
- Turnover time is a design target you choose, not a fixed property of the pool — a shorter turnover time demands a higher pump flow rate for the same volume.
- This page calculates volume and the flow a turnover target implies; it does not size chemical doses on its own — that's the companion pool chemical calculator's job, using the volume this page produces as its starting input.
The formula
average depth = (shallow depth + deep depth) ÷ 2; surface area = shape-specific formula; volume = surface area × average depth; gallons = volume × 7.48
- average depth
- The mean of the shallow-end and deep-end depths, used as a flat depth across the whole surface area — a working approximation for a sloped pool floor, not an exact volumetric integral of the actual slope.
- surface area
- The pool's water-surface footprint, calculated with a different formula depending on the shape selected — rectangular, round or oval — since these three shapes do not share one area formula.
- 7.48 gallons per cubic foot
- The standard conversion factor between cubic feet and US gallons, used to turn a geometric volume into the unit pool chemicals, pumps and fill times are all actually specified in.
- turnover time
- The target number of hours for a pump and filter to cycle the pool's entire volume once — a design choice, commonly somewhere between 6 and 10 hours for a residential pool, that directly sets the required pump flow rate.
Where these numbers come from
- 7.480519 gallons per cubic foot
- Standard, fixed unit conversion (US gallons), not an estimate — 1 cubic foot of water is exactly this many US gallons by definition of the two units.
- 3.785411784 litres per gallon
- Standard, fixed unit conversion (US gallon to litre), used only for the litres figure on this page as a reference for pools measured or discussed in metric terms.
- 6-10 hour turnover time
- Trade convention for residential pool circulation design — shorter turnover times filter and sanitize water more aggressively but demand a larger, more expensive pump; 8 hours is a common working middle ground, adjustable per pool based on bather load and local code guidance where it applies.
- Ellipse area approximation for oval pools
- Standard geometric approximation — a true oval pool's exact area depends on its specific curve, but treating it as an ellipse from its overall length and width gives a reasonably close estimate for volume-planning purposes.
Worked examples
A rectangular family pool, 32 by 16 feet
| Pool shape | Rectangular |
|---|---|
| Length or diameter | 32 ft |
| Width | 16 ft |
| Shallow end depth | 3 ft |
| Deep end depth | 6 ft |
| Target turnover | 8 |
| Pool volume | 17236 gallons |
|---|---|
| Surface area | 512 sq ft |
| Average depth | 4.5 ft |
| Volume | 2304 cu ft |
| Volume in litres | 65243 litres |
| Pump flow for turnover | 35.9 gpm |
| Perimeter | 96 ft |
512 sq ft of surface area at a 4.5 ft average depth (the midpoint of a 3 ft shallow end and a 6 ft deep end) comes to 2,304 cu ft, or just over 17,200 gallons. Using the 6 ft deep-end depth alone across the whole surface, instead of the average, would have overstated this pool by 33% — a third more water than actually exists, which matters directly to anyone dosing chemicals against volume.
Targeting an 8-hour turnover on this volume needs a pump moving about 36 gpm continuously — a figure worth having in hand before shopping for a pump and filter combination, since undersized equipment simply won't hit the target turnover time no matter how long it runs in a day.
A small round plunge pool, 14 foot diameter
| Pool shape | Round |
|---|---|
| Length or diameter | 14 ft |
| Width | 14 ft |
| Shallow end depth | 3 ft |
| Deep end depth | 4 ft |
| Target turnover | 4 |
| Pool volume | 4031 gallons |
|---|---|
| Surface area | 153.9 sq ft |
| Average depth | 3.5 ft |
| Volume | 538.8 cu ft |
| Volume in litres | 15257 litres |
| Pump flow for turnover | 16.8 gpm |
| Perimeter | 44 ft |
A round pool's area formula gives about 154 sq ft from a 14 ft diameter — noticeably less than the 196 sq ft a 14 by 14 ft square would cover, which is the general rule that a circle always holds less water than the square that circumscribes it. At a shallower 3.5 ft average depth, this plunge pool comes to just over 4,000 gallons, less than a quarter of the first example's volume.
The faster 4-hour turnover target common on smaller pools and spas needs less absolute pump flow than the family pool despite the shorter time window, simply because there's so much less total volume to move — proof that turnover time and pump size don't scale together in a simple way; total volume is doing most of the work in that calculation.
Common mistakes
- Using the deep-end depth as if it applied across the whole pool, which overstates volume substantially on any pool with a meaningful shallow-to-deep slope.
- Treating a round or oval pool's area as if it were the rectangle that circumscribes it — both shapes hold less water than their bounding rectangle, sometimes by 20% or more.
- Sizing a pump to a turnover time without first getting an accurate volume — pump sizing quotes are only as good as the volume figure feeding them, and a rough guess at volume produces a rough guess at pump size.
- Assuming a shorter turnover time is always better without weighing the larger pump and higher energy cost it requires — most residential pools don't need to chase the shortest possible turnover.
- Forgetting that a pool with a shallow sun shelf or tanning ledge doesn't fit the simple shallow/deep average depth model well — a pool with a large very-shallow area needs its volume estimated in sections rather than as one uniform average.
Shopping summary
Volume in gallons is the number to hand a pool-supply store or use directly in the pool chemical calculator — chemical dosing on this site and virtually everywhere else is specified per gallon or per 10,000 gallons, not per cubic foot or square foot of surface.
Pump and filter shopping should target at least the flow rate this page calculates for your chosen turnover time, though real system head loss (pipe length, fittings, filter resistance) means the pump's rated flow at your system's actual operating pressure — not its maximum rated flow on a spec sheet — is what needs to clear that number.
If the pool deck itself is also being poured or paved at the same time as the pool, that's a separate material calculation — the concrete slab calculator or paver calculator covers that work, and neither shares any arithmetic with the water volume calculated here. Many jurisdictions also require pool fencing before a permit closes out; the fence calculator prices that separately.
FAQ
Why does average depth understate my pool's volume less than I expected on a shallow pool?
Because the gap between average depth and maximum depth is proportional to how much the deep end actually exceeds the shallow end — a pool with only a foot or two of difference between shallow and deep ends has an average depth close to its maximum depth, while a pool with a dramatic drop-off (a 3 ft shallow end into an 8 or 9 ft deep end) sees a much bigger gap between the two.
How much less water does a round pool actually hold than a square one the same width?
A circle's area is about 78.5% of the area of the square that circumscribes it — so a round pool with a 14 ft diameter holds roughly 78.5% of the volume a 14 by 14 ft square pool at the same average depth would, a meaningful difference worth accounting for rather than approximating a round pool as square.
Does this calculator account for steps, benches or a sun shelf built into the pool?
Not directly — those features reduce the actual water volume relative to a simple average-depth calculation across the full footprint, since they displace water the way a large piece of furniture would. For a pool with substantial built-in features, treat this page's figure as a reasonable upper estimate and expect the true volume to run somewhat lower.
What turnover time should I actually target?
Residential pools commonly target somewhere between 6 and 10 hours; commercial and heavily used pools often target much faster turnover under local health-code requirements. Faster turnover generally means better water clarity and sanitizer distribution at the cost of a larger pump and higher energy use — there's a real tradeoff rather than one universally correct number.
Why do I need gallons instead of cubic feet for anything past this page?
Because chemical dosing, pump flow ratings and most pool-industry references are all specified in gallons, not cubic feet — cubic feet is the natural unit for the geometry calculation, but gallons is the unit everything downstream of this page (dosing, equipment sizing, fill time from a hose) actually uses.
Can I use this for an above-ground pool with a single, uniform depth?
Yes — enter the same value for both shallow and deep depth, which makes the average depth equal to the actual uniform depth, and the rest of the calculation works the same way for a rectangular, round or oval above-ground pool as it does for an in-ground one.
Where to go next
The projects this number is a step of, the guides that explain the method behind it, and the rest of its trade group.