How Much Do I Need?

Pool and Water Tank Volume Calculator

How much water does my pool hold?

Choose the shape, enter the size and the depth at the shallow and deep ends. The calculator works out the volume of water, shows it in every common unit and, if you add your hose flow rate, how long it will take to fill.

Units
Shape and size

Enter the same depth twice if the floor is flat.

Filling

How full, as a percentage of the depths above. Leave at 100% if you measured the water depth.

Time how long your hose takes to fill a bucket. Leave blank to skip the fill time.

Cost (optional)

Add the price to see an estimated total.

Results update as you type.

Your estimate

Water volume

15,990 gallons

60,527 litres. About 26.6 hours to fill.

Estimated amount needed

Water to fill
15,990 gallons
Time to fill
26.6 hours

Calculated volume

US gallons
15,990
Imperial (UK) gallons
13,314
Litres
60,527
Cubic metres
60.53
Cubic feet
2,137.5
Average depth
57 in
How this was calculated
  1. Surface = 30 ft × 15 ft = 450 ft²
  2. Average depth = (3.5 ft + 6 ft) ÷ 2 = 4.75 ft
  3. Volume = surface × average depth = 2,137.5 ft³
  4. 2,137.5 ft³ × 7.48 gallons per ft³ = 15,990 gallons
  5. Fill time = 15,990 gallons ÷ 10 gal per minute = 1,599 minutes (26.6 hours)
  • Water weighs about 8.34 lb per US gallon (1 kg per litre). Check that a raised deck or indoor floor can carry a hot tub or tank before filling it.
  • Pool chemical doses are based on this volume, so a close estimate matters. Follow the product label.

How the pool volume calculation works

  1. Surface area: rectangle = length × width; round = π × radius²; oval = π × (length ÷ 2) × (width ÷ 2).
  2. Average depth = (shallow end + deep end) ÷ 2. For a pool with a flat floor, both depths are the same.
  3. Volume = surface area × average depth × fill level.
  4. Units: 1 ft³ = 7.48 US gallons = 28.32 litres; 1 m³ = 1,000 litres = 264.17 US gallons; 1 imperial gallon = 4.546 litres.
  5. Fill time = volume ÷ flow rate.

Pools with sloped floors

Averaging the shallow and deep ends is exact for a floor that slopes evenly from one end to the other. Pools with a steep drop to a deep "hopper" section hold somewhat less than the average suggests, so for those it's more accurate to split the pool into sections and add them up.

Rounding rules

  • Volumes are shown to the nearest gallon or litre and are not rounded up. There is nothing to buy in whole units, and chemical doses need the real figure.
  • Fill time is shown to one decimal place of an hour.