Solve backwards
What size pool holds my gallons or litres?
- 20,000 galThe example worked below
- Pool Volume Calculator (Rectangular, Round, Oval or Kidney)Every figure is its own
You have
How much pool water?
That is 20,000 gal(75,708.2 L). Worked by the Pool Volume Calculator (Rectangular, Round, Oval or Kidney) at the settings below.
The settings it uses
- Pool Shape
- Rectangle
- Floor
- One depth: a flat floor, or an average depth you already know
- Average Depth
- 5 ft
What it will do
535 sq ft of water surface
49.7 m²
One pool. Enough for a pool 33 × 16 ft.
Or several. Less than one pool of the size the Pool Volume Calculator (Rectangular, Round, Oval or Kidney) opens on (a pool 33 × 17 ft).
Check it forwards
- Pool Length
- 32.7 ft
- Pool Width
- 16.4 ft
- It asks for
- 20,000 gal
- You have
- 20,000 gal
The Pool Volume Calculator (Rectangular, Round, Oval or Kidney) asks for 20,000 gal at that size.
If you had more, or less
Around your amount
Each worked by the Pool Volume Calculator (Rectangular, Round, Oval or Kidney) at the same settings.
Half
10,000 gal
267 sq ft
a pool 23.1 × 11.6 ft
Yours
20,000 gal
535 sq ft
a pool 33 × 16 ft
Half as much again
30,000 gal
802 sq ft
a pool 40 × 20 ft
Double
40,000 gal
1,069 sq ft
a pool 46 × 23 ft
Common amounts
What each amount of pool water covers
The sizes it is usually sold in, each worked by the Pool Volume Calculator (Rectangular, Round, Oval or Kidney) at the settings above.
| You have | It covers | As one pool | Average pools |
|---|---|---|---|
| 5,000 gal(18,927.1 L) | 134 sq ft(12.4 m²) | a pool 16.4 × 8.2 ft | under 1 |
| 10,000 gal(37,854.1 L) | 267 sq ft(24.8 m²) | a pool 23.1 × 11.6 ft | under 1 |
| 15,000 gal(56,781.2 L) | 401 sq ft(37.3 m²) | a pool 28.3 × 14.2 ft | under 1 |
| 20,000 gal(75,708.2 L) | 535 sq ft(49.7 m²) | a pool 33 × 16 ft | under 1 |
| 30,000 gal(113,562.4 L) | 802 sq ft(74.5 m²) | a pool 40 × 20 ft | 1 |
Seven and a half gallons a cubic foot
The calculator multiplies length, width and average depth in feet by 7.4805 US gallons per cubic foot, the exact 1,728 ÷ 231; a cubic metre is 1,000 litres. So 20,000 gallons at 5 feet deep is about 535 square feet of water, a pool about 32.7 by 16.4 feet, and 50,000 litres at 1.5 m is 33.3 m², about 8.2 by 4.1 m. A common 16 by 32 foot pool at a 5 foot average holds about 19,150 gallons.
Average depth is where it goes wrong
The average depth is applied flat across the whole plan. Averaging the shallow and deep ends is exact only where the floor falls at one steady rate end to end, or where the two sections cover equal plan area. On the usual layout — a large flat shallow end, a slope, then a smaller deep end — the plain average overstates the volume, so the same gallons really fill a slightly larger pool than this.
A capacity, not a dose
Steps, benches, ledges and coved corners take space this calculation fills with water, and the pipework, filter, heater and any attached spa hold more that the figure never sees. The volume is a capacity, not a dosing instruction: an overstated volume overdoses every time it is used, so dose once, circulate a full turnover, then test before dosing again — never twice off the same figure.
How the answer is worked
Nothing here is a second formula. The Pool Volume Calculator (Rectangular, Round, Oval or Kidney) runs forwards — a size in, a quantity out — and this page grows its own starting pool in proportion until the quantity it asks for is what you have. Where it rounds up to whole containers, the answer is the largest size before the next one would be needed.
Where the calculator adds an allowance for cuts or breakage when you order, the same allowance comes off here, because it is the same calculator: a stack you already own finishes less than its face value. Where it adds none, neither does this page — the settings beside the answer say which.
Pool Volume Calculator (Rectangular, Round, Oval or Kidney)
runs it forwardsThe water a rectangular, round, oval or kidney-shaped pool holds over a flat or sloping floor, in litres or US gallons, for dosing and filling it.
Work out what to buy insteadSolve backwards
Other things you might already have
How much roof fills my rain barrel in an inch of rain?
Rain barrel, worked by the Rain Barrel and Rainwater Collection Calculator.
Solve backwards
Start from what is already in the yard
Paint, sheets, rolls, bags and pieces, each read the other way by the calculator that orders it.
The calculator's own figures
Nothing is estimated twice: the page runs the same calculator you would order with.
The largest size that fits
Where a calculator rounds up to whole containers, the answer stops before the next one.
Both unit systems
Gallons and litres, square feet and square metres, side by side.
Frequently asked questions
- How much water surface does 20,000 gal of pool water cover?
- At the Pool Volume Calculator (Rectangular, Round, Oval or Kidney)'s own settings, 535 sq ft (49.7 m²) — a pool 33 × 16 ft. Every figure follows the settings, which you can change in the calculator.
- How much water surface does 50,000 L of pool water cover?
- At the Pool Volume Calculator (Rectangular, Round, Oval or Kidney)'s own settings, 33.3 m² (359 sq ft) — a pool 8.2 × 4.1 m. Every figure follows the settings, which you can change in the calculator.
- How many gallons is a 16 by 32 pool?
- At a 5 foot average depth, 16 × 32 × 5 is 2,560 cubic feet, about 19,150 gallons (72,500 litres) at the calculator's 7.4805 gallons per cubic foot. At a 4.5 foot average it is about 17,240 gallons. Steps and benches take some of that out.
- How do I find the average depth of a pool?
- Add the shallow-end and deep-end depths and halve them — 3.5 and 8 feet average 5.75 (1.07 and 2.44 m average 1.75 m). That is exact only where the floor slopes evenly end to end; with a large flat shallow end and a small deep end, weight each section by its area instead.
- How many litres is a 10 by 5 metre pool?
- At a 1.5 m average depth, 10 × 5 × 1.5 is 75 m³ — 75,000 litres, about 19,800 US gallons. At a 1.2 m average it is 60,000 litres. A cubic metre is exactly 1,000 litres, which is why metric pool volumes are the easier ones to work out.