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Hot tubs, pools, and the machines that clean them

Pool Robotic

Pool Volume Calculator

Pool Shape And Size
Depth
Measure the water, not the wall height.
Filling

Pool volume, rectangle 32 × 16 ft, 5 ft average depth

19,150 gal

Liters72,491 L
Cubic meters72.5 m³
Cubic feet2,560 cu ft

Fill time at 9 GPM: 35 h 28 min (2,128 min)

Water cost to fill: —

32 × 16 × 5 = 2,560 cu ft × 7.48052 gal/cu ft

Formulas used (volume in cubic feet, then × 7.48052 gal per cu ft)
ShapeVolume formulaNote
RectangleLength × Width × Average depthExact for a true rectangle
Roundπ × (Diameter ÷ 2)² × Average depthIndustry pages write 3.14 for π
Ovalπ ÷ 4 × Length × Width × Average depthApproximation: treats the pool as an ellipse
Kidney0.45 × (Width A + Width B) × Length × Average depthApproximation: A and B are the two widest points
Average depth(Shallow end + Deep end) ÷ 2Assumes a straight slope between the two ends
Fill timeGallons ÷ hose flow (gal/min)L/min ÷ 3.785412 = gal/min

Sources: shape formulas and the average-depth rule from Swimmingpool.com (Pool Corporation) and Leslie's pool volume guide, which round the conversion to 7.5 gal per cu ft; this tool uses 7.48052, from NIST SP 811 Appendix B.9 (1 ft³ = 0.02831685 m³, 1 US gal = 0.003785412 m³). Oval and kidney results are approximations. Accessed 2026-09-14.

How It Works

The calculator finds the pool’s volume in cubic feet from its shape, then converts to US gallons at 7.48052 gallons per cubic foot (from the NIST conversion factors: 1 cubic foot = 0.02831685 m³, 1 US gallon = 0.003785412 m³). Liters and cubic meters follow from the same factors. Metric dimensions are converted at 0.3048 m per foot before the volume is computed.

The shape formulas are the standard pool-industry ones published by Swimmingpool.com and Leslie’s: rectangle is length × width × average depth; round is π × radius² × average depth; oval is π ÷ 4 × length × width × average depth; kidney is 0.45 × (width A + width B) × length × average depth, where A and B are the two widest points. Industry pages round π to 3.14 and the conversion to 7.5 gal per cubic foot, so their totals run about 0.3% higher than this tool’s. The oval and kidney formulas are approximations of real pool outlines.

If the pool has a shallow and a deep end, average depth is (shallow + deep) ÷ 2, which assumes a steady slope. Measure water depth, not wall height. Fill time is gallons ÷ hose flow in gallons per minute (L/min ÷ 3.785412). Water cost is gallons ÷ 1,000 × your utility’s rate per 1,000 gallons; leave the rate blank and the tool shows a dash.

Worked Example

A 32 × 16 ft rectangular pool with a 3 ft shallow end and a 7 ft deep end has an average depth of 5 ft. Volume is 32 × 16 × 5 = 2,560 cubic feet, which is 2,560 × 7.48052 = 19,150 US gallons (72,491 L, 72.5 m³). A garden hose at 9 gallons per minute fills it in 19,150 ÷ 9 = 2,128 minutes, or 35 hours 28 minutes.

FAQ

How accurate is this?

For a true rectangle or circle with the measured depths, it is as accurate as your tape measure. Oval and kidney pools use standard approximations; expect a few percent either way. A sloped floor with a hopper (a steep deep end) holds less than the straight-slope average suggests.

Why does my pool store’s number differ?

Most pool-industry calculators use 7.5 gallons per cubic foot instead of 7.48, and 3.14 for π. That makes their figure about 0.3% larger. Either is fine for chemical dosing.

How fast does a garden hose fill a pool?

Household hoses typically deliver somewhere around 5–10 gallons per minute depending on pressure and hose diameter. Time a bucket: fill a 5-gallon bucket, note the seconds, and enter 300 ÷ seconds as your flow in gallons per minute.

Should I use the wall height or the water depth?

Water depth. Pools are not filled to the rim, and chemical doses depend on the water actually in the pool.

What is the volume in liters or cubic meters?

The tool shows both. One US gallon is 3.785412 liters, and 1,000 liters is one cubic meter.

Sources