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Pool Volume Calculator: How Many Gallons Is My Pool?

Work out how many gallons of water a pool or hot tub holds from its shape, size and depth, and what it costs to fill. Pick rectangle, round, oval, kidney or hot tub, enter one depth or the shallow and deep end, and get gallons, cubic feet and liters, plus the fill time from a hose and the water cost.

Your numbers

ft
ft
ft

Measure the water, not the wall. Use feet with decimals: 4 ft 6 in = 4.5.

gpm

Typical value, measure yours with a bucket: gallons in the bucket ÷ minutes to fill it.

$

Optional. From your water bill, in the unit chosen; there is no default.

Pool volume

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In cubic feet
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In liters
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Surface area
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Average depth
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Fill time at 10 gpm
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Water cost to fill
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An estimate from your measurements: steps, benches and a hopper-shaped deep end change the real volume.

For chemicals, follow the product label for your volume.

The calculation runs in your browser and ParrotNotes does not store your numbers. They sit in the page address so you can bookmark or share the result.

How many gallons is my pool?

A pool's volume is its surface area × its average depth. Measure the length and width of the water in feet, work out the area, multiply by the average depth for cubic feet, then multiply by 7.48 for US gallons. NIST defines the US gallon as 231 cubic inches, so a cubic foot (1,728 cubic inches) holds 7.480519 gallons, or 28.32 liters.

Worked example: a 32 × 16 ft rectangle that slopes from 3.5 ft at the shallow end to 8 ft at the deep end averages 5.75 ft. That is 512 square feet × 5.75 = 2,944 cubic feet, or about 22,023 gallons (83,365 liters).

Pool gallons calculator for round, oval and kidney pools

Round pools, above-ground or in-ground: π × (diameter ÷ 2)² × depth. A 24 ft round pool with 4 ft of water is 452.4 square feet × 4 = 1,809.6 cubic feet, about 13,536 gallons.

Oval pools are worked out as an ellipse, π × half the length × half the width (the area formula on Wolfram MathWorld). A 30 × 15 ft oval at 4.5 ft holds about 11,897 gallons. Many above-ground ovals have straight sides; those hold a little more than the ellipse of the same length and width, so treat the result as a floor.

Kidney and free-form pools have no single formula. The calculator takes the length and the widest and narrowest widths and uses the average width: 30 ft long, 16 ft and 12 ft wide, 5 ft deep is 420 square feet × 5 = 2,100 cubic feet, about 15,709 gallons. For an odd shape, split it into rectangles and circles, work out each one and add them up.

Shallow end and deep end: the average depth

Pick 'Shallow and deep end' and enter the water depth at each end. The calculator uses (shallow + deep) ÷ 2, which is right when the floor slopes evenly. Measure the water, not the wall: the water line usually sits below the top of the wall.

Many in-ground pools have a long shallow area and a short deep hopper. For those, the average overstates the volume; split the pool into a shallow rectangle and a deep one and add the two.

Hot tubs and spas

Pick Hot tub / spa, then round or square, and enter the inside size and the water depth. A round tub 7 ft across with 3 ft of water works out at about 864 gallons; a square 7 × 7 ft tub at 3 ft at about 1,100.

Seats, steps and the footwell take up room, so a real tub holds less than that box. The maker's spec sheet gives the capacity; use the calculator when the sheet is lost or the tub is built in.

Fill time and what the water costs

Fill time is gallons ÷ the hose flow. Iowa State University Extension describes the bucket test: time how long the hose takes to fill a five-gallon bucket and divide 5 by the minutes. The calculator starts at 10 gallons a minute as a typical value; your pressure, hose and nozzle decide the real flow, so measure it. Two hoses on two taps roughly halve the time if the pressure holds.

For the cost, type the price from your water bill. If the bill prices water per 1,000 gallons, keep that unit; if it uses CCF (100 cubic feet, about 748 gallons), switch the unit. Ask the utility about sewer charges on pool water before you quote the number to a customer.

Chemicals: dose for the volume

Chlorine, shock, pH adjusters and algaecides give their doses per gallons or liters of water. Use the volume from this page with the product label, and recheck it after a refill or a resurfacing. The label wins over any rule of thumb.

On the service call

For pool service techs and pool sales reps the volume is the first line of the job sheet: it sizes the chemical order, the pump and filter conversation and the quote for a refill. Measure it once, write it on the account, and you are not guessing on every visit.

The rest of the visit is what the owner says: the cloudy water after the last storm, the pump that hums, when the kids are home, the budget for a heater. Those notes decide the next visit as much as the gallons do.

Sources, checked October 2026. All results are estimates:

More for home-services and route sales: Door-to-door sales, Pest control sales, AI note taker for in-person meetings.

The gallons are the easy part

On a service call or a sales visit, the owner tells you about the cloudy water, the noisy pump, the leak they suspect and when they want the pool open. Record the visit in ParrotNotes and get a summary and next steps, so the quote and the next visit match what they asked for.

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Pool volume calculator FAQ