Pool Ratio

20 × 40 ft pool: how many gallons?

A 20 × 40 ft pool with 3.5 ft shallow end, 6 ft deep end holds about 28,430 US gallons (107,604 litres). Here is what that means for salt and chemicals.

Last updated · Checked against published product doses · How we calculate

Volume
28,430 gal
107,604 litres · 3.5 ft shallow end, 6 ft deep end
Salt to 3,200 ppm (new salt pool)759 lb · 19 × 40 lb bags
10% liquid chlorine per +1 ppm36 fl oz
Stabilizer 0 → 40 ppm9.5 lb
Baking soda per +10 ppm alkalinity4 lb
Calcium chloride (77%) per +10 ppm55 oz

Open the chemical calculator for this pool →

The maths

  1. Average depth = (3.5 + 6) ÷ 2 = 4.75 ft
  2. Volume = 40 × 20 × 4.75 = 3,800 cu ft
  3. 3,800 cu ft × 7.48 gal per cu ft

= 28,430 US gallons

Real pools vary: water levels sit a few inches below the wall top, floors slope and corners are rounded. If your pool’s depth differs, adjust it in the volume calculator.

Frequently asked questions

How many gallons is a 20 × 40 ft pool?

About 28,430 US gallons (107,604 litres) with 3.5 ft shallow end, 6 ft deep end.

How much salt does a 20 × 40 ft pool need?

About 759 lb (344 kg) to bring fresh water to 3,200 ppm, or 19 bags of 40 lb. Check your salt cell’s target first.

How much chlorine does a 20 × 40 ft pool need?

Each +1 ppm of free chlorine takes about 36 fl oz of 10% liquid chlorine. With stabilizer at 40 ppm, keep free chlorine around 4.6 ppm.

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