POOL VOLUME CALCULATOR

Pool Volume Calculator — Gallons & Litres for Any Pool Shape

Calculate your swimming pool volume in litres or gallons. Supports rectangular, circular and L-shaped pools. Enter the surface dimensions and shallow and deep end depths to get an accurate volume estimate for chemical dosing, pump sizing and fill time planning.

Pool shape

Dimensions (m)

Depth (m)

Pool volume
—litres

Enter pool dimensions to calculate volume.

Find Your Pool Volume in Gallons or Litres for Any Pool Shape

The Interior Tailor Pool Volume Calculator works out how much water your swimming pool holds, in gallons or litres. Choose rectangular, circular or L-shaped, enter the surface dimensions and the shallow and deep end depths, and get an estimate you can use for chemical dosing, pump sizing and fill time planning. Because it uses the average depth of a sloped floor, it gives a more realistic result than a simple length by width by depth guess.

What the Pool Volume Calculator Includes

  • Three pool shapes: rectangle or square, circle, and L-shape. For an oval pool, calculate its surface area separately.
  • Sloped floor support: enter shallow and deep end depths so the calculator uses the average depth.
  • Metric or imperial: metres and litres, or feet and gallons.
  • Pump turnover estimate: see how volume relates to turnover time when sizing a pump.
  • Planning-ready result: use the volume for chemical dosing, heating and fill time.

How Pool Volume Is Calculated

For a pool with a sloped floor, average depth is used:

Average Depth = (Shallow End + Deep End) ÷ 2

Volume (ft³) = Surface Area × Average Depth

Volume (gallons) = ft³ × 7.48052

For L-shaped pools, calculate the two rectangular sections separately and add their surface areas together before multiplying by the average depth. For oval and kidney pools, estimate the surface area separately using a formula suited to the shape.

Why Knowing Your Pool Volume Matters

  • Chemical dosing: Chlorine, shock, algaecide, pH adjusters and stabilizer are all dosed per 10,000 gallons — an incorrect volume leads to over- or under-dosing
  • Pump sizing: Your pump and filter should turn over the entire pool volume every 6–8 hours. A 20,000-gallon pool needs a pump rated at 2,500–3,300 GPH minimum.
  • Heating cost: It takes approximately 1 BTU to raise 1 pound of water (8.34 lb/gal) by 1°F. A 20,000-gallon pool requires about 1,668,000 BTU to raise temperature by 10°F.
  • Salt chlorine systems: Salt chlorinators are sized by pool volume — use the correct cell size for your pool

Pool Volume Quick Reference

  • 12×24 ft rectangular, 3.5–5 ft depth: ~9,160 gallons
  • 16×32 ft rectangular, 3.5–6 ft depth: ~18,190 gallons
  • 18×36 ft rectangular, 3.5–8 ft depth: ~27,870 gallons
  • 24 ft round, 4 ft depth: ~13,600 gallons
  • 27 ft round, 4 ft depth: ~17,200 gallons
  • 15×30 ft oval, 4 ft depth: ~10,600 gallons

Pool Projects You Can Plan

Use the volume result for:

  • Chemical dosing for chlorine, shock, algaecide and pH adjusters
  • Pump and filter sizing
  • Salt chlorinator selection
  • Heating and fill-time planning
  • Comparing pool sizes before you build or buy

Example Pool Volume Calculations

These examples use the page's formula: volume = surface area x average depth, and gallons = cubic feet x 7.48052.

Example Pool Volume Calculations
PoolInputsAverage depthVolume
Rectangular16 ft x 32 ft, 3.5 ft to 6 ft deep4.75 ft2,432 cu ft, about 18,190 gal
Round24 ft diameter, 4 ft deep4 ft1,810 cu ft, about 13,540 gal
L-shaped (two sections)20 ft x 10 ft plus 10 ft x 10 ft, 5 ft average depth5 ft1,500 cu ft, about 11,220 gal
Metric rectangular8 m x 4 m, 1 m to 2 m deep1.5 m48 cu m, 48,000 litres

Pump turnover example: an 18,190 gallon pool turned over every 6 to 8 hours needs about 2,270 to 3,030 gallons per hour.

Tips for an Accurate Pool Volume

  • Measure the water surface, not the outer pool wall, and use the average of the shallow and deep end depths.
  • Measure the actual water depth, not the pool wall height.
  • For L-shaped pools, split the pool into two rectangles. The calculator's L-shape option handles this for you.
  • For kidney and freeform pools, treat the result as an estimate and measure actual fill with a water meter if you need precision.
  • Re-check your volume before chemical dosing, since an incorrect volume causes over- or under-dosing.

Frequently Asked Questions

How long does it take to fill a pool?

A standard garden hose flows approximately 9 gallons per minute. A 20,000-gallon pool takes about 2,222 minutes (37 hours) to fill at that rate. A faster ¾-inch hose at 15 GPM takes about 22 hours.

How accurate is an estimated pool volume?

Calculated volumes are estimates. For precise chemical dosing, measure actual water used during the fill with a water meter. Kidney and freeform pools are particularly difficult to estimate accurately.

How much does it cost to fill a pool?

At an average US water rate of $0.005 per gallon, a 20,000-gallon pool costs approximately $100 to fill from municipal water. Rates vary significantly — check your utility bill for your actual rate per 1,000 gallons.

How do I calculate pool volume for a pool with a sloped floor?

Find the average depth by adding the shallow and deep end depths and dividing by two. Multiply the surface area by that average depth for cubic feet, then multiply by 7.48052 to convert to gallons.

Why do I need to know my pool volume for chemicals?

Chlorine, shock, algaecide, pH adjusters and stabilizer are all dosed by volume of water, commonly per 10,000 gallons. A wrong volume leads to under- or over-dosing, so always follow the product label for your exact volume.

How long should my pump run to turn over the pool?

A common target is to turn over the full pool volume every 6 to 8 hours. Divide your volume by the hours to find the flow rate you need in gallons per hour.