Pool Volume Calculator – Find Your Pool’s Exact Water Capacity in Seconds
Knowing your pool’s exact water volume isn’t just a nice-to-have — it’s the foundation of every pool care decision you make. Chlorine, shock, algaecides, pH adjusters, and stabilizers are all dosed by the gallon. Guess wrong, and you’re either wasting money on excess chemicals or under-dosing — leaving your water vulnerable to algae blooms and bacteria. Pool volume also determines your pump and filter sizing, how long to run your circulation system, and what it costs to fill or top up your pool.
Our free calculator handles seven pool shapes — rectangular, L-shaped, circular, triangular, kidney, oval, and oblong — with instant results in US gallons, UK gallons, liters, and cubic meters. Pick your shape, enter a few measurements, and you’ll get a precise volume estimate plus shock treatment dosing and water-fill cost estimates for your region. No sign-up, no spreadsheets — just accurate pool math, powered by standard geometric formulas.
Quick jump: Want a ballpark number instead? Jump to our Quick Reference Table with pre-calculated volumes for the 16 most common pool sizes.
Shock Treatment Recommendation
Estimated Water Cost (Initial Fill)
Fill Time Estimate
Typical garden hose: 6–12 GPM. Not sure? Try a bucket test: time how many seconds to fill a 5-gallon bucket, then divide 300 by the seconds.
Pool Volume Formulas
Rectangular (Constant Depth)
1 ft³ = 7.5 US gallons
Rectangular (Variable Depth)
If slope is gradual and even
Circular
π ≈ 3.14
Triangular (Right Angle)
Oval
(Ellipse area)
Kidney
Davg = (Deep End + Shallow End) / 2
Industry standard approximation for kidney-shaped pools
L-Shaped
Side Area = (Total Width − Short Arm Width) x Short Arm Length
Decompose the L into two rectangles
Oblong
Lrect = Overall Length − W
Rectangle + two semicircles (one full circle)
- 1 cubic foot (ft³) = 7.48 US gallons
- 1 ft³ = 6.23 UK gallons
- 1 ft³ = 28.32 liters
- 1 m³ = 1000 liters
- 1 gallon of water ≈ 8.33 lbs
- 1 inch = 0.0833 ft
Pool Volume Quick Reference Chart — US Gallons by Size & Depth
Find your pool size below and scan across to your water depth. All volumes in US gallons. For litres, multiply by 3.785 (or use the calculator above for instant conversion to UK gallons, litres, and m³). Above-ground depths shown are water depth (wall height minus ~6 inches). In-ground depths are the average of shallow and deep ends. Stock tanks (8′–12′ round) are popular budget-friendly mini-pools; typical water depth is 24″–30″.
| Shape | Dimensions | 30″ | 36″ | 42″ | 48″ | 52″ |
|---|---|---|---|---|---|---|
| Above-Ground Pools — Gallons at Water Depth | ||||||
| Round | 8′ diam | 940 | 1,150 | — | — | — |
| Round | 10′ diam | 1,450 | 1,750 | 2,050 | — | — |
| Round | 12′ diam | 2,100 | 2,550 | 2,950 | 3,400 | — |
| Standard Above-Ground Pools | ||||||
| Round | 15′ diam | 3,300 | 3,950 | 4,650 | 5,300 | 5,700 |
| Round | 18′ diam | 4,750 | 5,700 | 6,700 | 7,600 | 8,200 |
| Round | 24′ diam | 8,500 | 10,200 | 11,800 | 13,500 | 14,700 |
| Rectangular | 12′ x 24′ | — | 6,500 | 7,500 | 8,600 | 9,300 |
| Rectangular | 15′ x 30′ | — | 10,100 | 11,800 | 13,500 | 14,600 |
| Oval | 12′ x 24′ | — | 5,100 | 5,900 | 6,800 | 7,300 |
| Oval | 15′ x 30′ | — | 7,900 | 9,300 | 10,600 | 11,500 |
| Shape | Dimensions | 4′ avg | 4.5′ avg | 5′ avg | 5.5′ avg | 6′ avg |
|---|---|---|---|---|---|---|
| In-Ground Pools — Gallons at Average Depth | ||||||
| Rectangular | 12′ x 24′ | 8,600 | 9,700 | 10,800 | 11,800 | 12,900 |
| Rectangular | 16′ x 32′ | 15,300 | 17,200 | 19,200 | 21,100 | 23,000 |
| Rectangular | 18′ x 36′ | 19,400 | 21,800 | 24,200 | 26,700 | 29,100 |
| Rectangular | 20′ x 40′ | 23,900 | 26,900 | 29,900 | 32,900 | 35,900 |
| Kidney | 16′ x 30′ | 9,800 | 11,000 | 12,200 | 13,400 | 14,600 |
| Oval | 18′ x 36′ | 15,200 | 17,100 | 19,000 | 20,900 | 22,800 |
How to read this chart: Find your pool shape and dimensions in the left columns, then scan right to the column matching your water depth. For example, a 24′ round above-ground pool at 52″ water depth holds 14,700 gallons; at 48″ it holds 13,500 gallons. A 16′ x 32′ rectangular in-ground pool with a 5′ average depth holds 19,200 gallons; with a 6′ average depth it holds 23,000 gallons.
Litres: Multiply any gallon number by 3.785 — e.g., 14,700 gal × 3.785 = 55,600 L. UK gallons: Multiply by 0.833. Cubic meters: Divide litres by 1,000.
Frequently Asked Questions About Pool Volume
A 15-foot diameter round above-ground pool with 48 inches of water holds approximately 5,300 US gallons (about 20,000 litres). The exact amount depends on your actual water level. A 15-foot pool filled to only 42 inches holds about 4,600 gallons, while the same pool at 52 inches holds roughly 5,700 gallons. For a precise number, use the calculator above with your exact measurements.
A 24-foot diameter round above-ground pool with 52 inches of water holds approximately 14,600 US gallons (about 55,300 litres). This is one of the most common large above-ground pool sizes. If your water level is lower — say 48 inches — the volume drops to about 13,500 gallons. Always measure from the water surface to the floor, not the top rail.
A standard 16-foot by 32-foot rectangular inground pool with a 5-foot average depth holds approximately 19,100 US gallons (72,300 litres). For a pool with 3-foot shallow end and 8-foot deep end, the average depth is 5.5 feet, giving you about 21,100 gallons. Most 16 x 32 inground pools fall between 18,000 and 22,000 gallons depending on the depth profile.
A 20-foot by 40-foot rectangular pool with a 5-foot average depth holds 30,000 US gallons (113,600 litres). This is the classic large inground pool size. At a 6-foot average depth (e.g., 3.5 ft shallow / 8.5 ft deep), the volume increases to about 36,000 gallons. Use our Quick Reference Chart above for side-by-side comparisons of common pool dimensions.
A US gallon equals 3.785 litres (128 fluid ounces), while a UK (imperial) gallon equals 4.546 litres (160 fluid ounces). To convert: multiply US gallons by 0.833 to get UK gallons, or multiply UK gallons by 1.201 to get US gallons. Our calculator displays both side by side so you do not need to do the math manually. Always check which gallon your chemical product uses — US brands use US gallons, while UK, Canadian, and Australian products often reference imperial gallons or litres.
For irregular pools without a standard geometric shape, use these practical methods: 1) Approximate with the closest shape — most freeform pools can be estimated as a kidney or oval, which our calculator supports. 2) Break into sections — mentally divide the pool into rectangles, circles, and triangles, calculate each separately, then add them. 3) The water meter method — for an exact measurement (especially useful during an initial fill), record your water meter reading before and after filling. Subtract normal household usage for the period. Each cubic foot of water is 7.48 gallons.
The cost depends on your pool size, local water rates, and whether you use a garden hose or a water delivery service. In the US, municipal water typically costs $0.003–$0.015 per gallon, so filling a 20,000-gallon pool runs about $60–$300. Truck delivery (bulk water) costs $0.03–$0.10 per gallon — $600–$2,000 for the same pool, but fills much faster. In Europe, water rates are higher: Germany averages €5–€10 per cubic meter (1,000 litres), and France €4–€5 per m³. Our calculator estimates costs for seven regions automatically when you enter your dimensions.
Multiply US gallons by 3.785 to get litres. For example: 10,000 US gallons x 3.785 = 37,850 litres. To go the other way, divide litres by 3.785. Our calculator has a built-in toggle — switch between US/UK gallons and litres/cubic meters with one click after calculating. If you are entering dimensions in meters rather than feet, use the Feet / Meters toggle in Step 3 before typing your measurements.
