Pool Volume Calculator
Pick the shape, enter the dimensions and the shallow and deep depths. You get the gallons and litres, the surface area for heater and cover sizing, and what it costs and how long it takes to fill from a hose.
Same as shallow for a flat-bottom pool.
From your water bill; US average is about $6.
A garden hose is 6-10 gpm; two hoses double it.
Volume
22,023 gal
83,365 litres
Surface area
512 sq ft
for heater and cover sizing
Cost to fill
$132
at $6/1,000 gal
Fill time
45.9 h
at 8 gpm (1.9 days)
32 × 16 × 5.75 ft average depth × 7.48 gal/ft³
Rectangular in-ground pools
Gallons by size and depth profile. "3.5 to 8" is the classic diving-pool profile; "4 to 6" a play pool; "flat 4" a sport pool.
| Size (ft) | Surface sq ft | Flat 4 ft | 4 to 6 ft | 3.5 to 8 ft |
|---|---|---|---|---|
| 12 × 24 | 288 | 8,618 | 10,772 | 12,388 |
| 14 × 28 | 392 | 11,729 | 14,662 | 16,861 |
| 15 × 30 | 450 | 13,465 | 16,831 | 19,356 |
| 16 × 32 | 512 | 15,320 | 19,150 | 22,023 |
| 18 × 36 | 648 | 19,390 | 24,237 | 27,872 |
| 20 × 40 | 800 | 23,938 | 29,922 | 34,410 |
Round above-ground pools
| Diameter | Surface sq ft | 42 in. water | 48 in. water | 52 in. water |
|---|---|---|---|---|
| 12 ft | 113 | 2,961 | 3,384 | 3,663 |
| 15 ft | 177 | 4,627 | 5,288 | 5,724 |
| 18 ft | 254 | 6,662 | 7,614 | 8,242 |
| 21 ft | 346 | 9,068 | 10,364 | 11,219 |
| 24 ft | 452 | 11,844 | 13,536 | 14,653 |
| 27 ft | 573 | 14,991 | 17,132 | 18,545 |
| 30 ft | 707 | 18,507 | 21,151 | 22,896 |
The formulas
- Rectangle: length × width × average depth × 7.48.
- Round: 3.14 × (diameter ÷ 2)² × depth × 7.48. Or diameter² × depth × 5.9.
- Oval: length × width × 0.785 × depth × 7.48. The 0.785 is π ÷ 4, the share of a rectangle an ellipse fills.
- Kidney / freeform: (wide width + narrow width) × length × 0.45 × depth × 7.48. The 0.45 is the industry estimate; measure the water at first fill for the real figure.
- Average depth: (shallow + deep) ÷ 2 assumes a straight slope. A pool with a long shallow shelf and a short deep hopper holds less; a rough fix is to weight the average toward the shallow end.
- Litres: gallons × 3.785. Cubic metres: litres ÷ 1,000.
Frequently Asked Questions
How many gallons is my pool?
Length × width × average depth × 7.48. A 16 × 32 ft rectangle with a 3.5 ft shallow end and 8 ft deep end averages 5.75 ft deep: 16 × 32 × 5.75 × 7.48 = 22,023 gallons. Round pools use π × radius² × depth × 7.48; ovals multiply length × width by 0.785; kidney shapes use the two widths added together × length × 0.45.
How many gallons is an 18 ft round above-ground pool?
7,614 gallons at 48 in. of water, 8,242 at 52 in. A 24 ft round at 48 in. is 13,536; a 15 × 30 oval at 48 in. is 10,570. Use the water depth, not the wall height: a 52 in. wall usually holds about 48 in. of water.
Why does the volume matter?
Every chemical dose is per 10,000 gallons, so a 20% error in volume is a 20% error in every dose you ever add. It also sizes the pump and filter (turnover in 6-8 hours), the heater, and the salt for a chlorine generator. Measure once, carefully, and write it on the equipment pad.
How long does it take to fill a pool?
Gallons ÷ hose flow. A garden hose delivers 6 to 10 gallons a minute, so a 22,023-gallon pool takes 46 hours at 8 gpm -- about 1.9 days. Two hoses halve it. A water truck delivers 6,000-9,000 gallons a load.
What does it cost to fill a pool?
Gallons ÷ 1,000 × your rate. At the US average of about $6 per 1,000 gallons, a 22,023-gallon fill is around $132, plus sewer charges if your utility bills them on water used (many will waive sewer for a documented pool fill if you ask).
These calculators use published seeding rates, extension-service fertilizer guidance, and standard pool-chemistry dosing figures, and are for planning. Read the product label; it governs the dose. Pool chemicals are hazardous when mixed or mishandled, and a pool store's water test beats any estimate here.