Pool Volume Calculator
Enter your pool’s length and width (or diameter) and average depth to calculate water volume in gallons, plus the liner size and fill cost you’ll need.
Average the shallow and deep end depths if the floor slopes.
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Filling tips
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Volume & size
Liner profile
A 24 × 12 ft rectangular pool with a 5 ft average depth holds about 10,772 gallons. That pool needs a 35 × 23 ft liner (805 sq ft) costing roughly $2,013, plus about $43 to fill with water.
Pool volume and liner size by pool dimensions
Volume assumes a rectangular or circular pool with a constant average depth; liner sizing uses a 1 ft PVC overlap allowance.
| Pool shape & size | Average depth | Water volume | Liner needed |
|---|---|---|---|
| Rectangular pool, 16 × 32 ft | 5 ft | 19,150 gal | 1,161 sq ft |
| Rectangular pool, 12 × 24 ft | 4.5 ft | 9,695 gal | 748 sq ft |
| Circular pool, 18 ft diameter | 4 ft | 7,614 gal | 729 sq ft |
| Rectangular pool, 20 × 40 ft | 5.5 ft | 32,914 gal | 1,664 sq ft |
| Circular pool, 24 ft diameter | 4.5 ft | 15,229 gal | 1,156 sq ft |
| Rectangular pool, 15 × 30 ft | 5 ft | 16,831 gal | 1,066 sq ft |
How to calculate pool volume in gallons
- Measure your pool's length and width. For rectangular and oval pools, measure at the water line; for round pools, measure the diameter across the surface.
- Measure or average the depth. If the floor slopes from shallow to deep end, average the two depths — (shallow + deep) ÷ 2 — for an accurate volume.
- Calculate the surface area. Multiply length × width for a rectangle, or π × (diameter ÷ 2)² for a circle.
- Convert to cubic feet, then gallons. Multiply area by average depth for cubic feet, then multiply by 7.48052 to convert to gallons.
- Size the liner and estimate fill cost. Add twice the depth plus overlap to each dimension for liner size, then multiply gallons by your water rate for fill cost.
Worked example
Using the calculator’s defaults: a 24 × 12 ft rectangular pool, 5 ft average depth, reinforced PVC liner at $2.50/sq ft, and fill water at $4 per 1,000 gallons.
- Pool dimensions24 ft × 12 ft
- Surface area (24 × 12)288 sq ft
- Average depth5 ft
- Volume (288 × 5)1,440 cubic ft
- Volume in gallons (1,440 × 7.48052)10,771.9 gal
- Liner size needed (L+2×depth+overlap × W+2×depth+overlap)35 ft × 23 ft = 805 sq ft
- Estimated liner cost (805 × $2.50)$2,012.50
- Estimated fill cost (10,771.9 gal × $4/1,000 gal)$43.09
Choosing a pool liner material
Match liner thickness and material to your pool’s size, usage, and how long you want it to last before replacement.
- Vinyl pool liner (20-28 mil)The standard choice for most above-ground and in-ground vinyl pools — balances cost and durability for typical residential use.
- Reinforced PVC pool linerA heavier-duty option for in-ground pools or high-traffic areas — better resistance to punctures, UV fading, and stretching over time.
- Match thickness to pool size and use.Larger pools and those with more foot traffic benefit from thicker, reinforced liner that holds up better to stress and wear.
- Plan liner replacement timing.Most vinyl pool liners last 6-12 years depending on climate, chemical balance, and UV exposure — budget for eventual replacement.
- Don't forget the pool floor pad.A separate cushioned underlayment beneath the liner protects it from ground irregularities and extends its usable life.
Common mistakes
- Using deep-end depth instead of average depth.Sloped pools hold much less water than deep-end-depth × area suggests — always average the shallow and deep end depths.
- Forgetting the liner overlap allowance.Liner cut to the exact pool dimensions won’t reach the coping or bead track — add depth and an overlap margin to both dimensions.
- Mixing up diameter and radius for round pools.The circle area formula needs the radius (half the diameter) — using the full diameter overstates area by 4x.
- Ignoring steps, benches, and other floor features.Built-in steps and tanning ledges reduce usable water volume slightly compared to a flat-floor calculation.
- Underestimating fill cost for large pools.A single fill can run into thousands of gallons — check your water utility’s rate before committing to a fill schedule.
- Buying liner sized to pool gallons instead of dimensions.Liner is sold and cut by square footage, calculated from length, width, and depth — not from the pool’s water capacity.
What this calculator assumes
Adjust your result if your project differs from these.
- Pool volume is calculated using the pool’s average depth, so sloped-floor pools should use (shallow depth + deep depth) ÷ 2.
- Rectangular pools use length × width × depth; circular pools use π × (diameter/2)² × depth.
- 1 cubic foot of water equals 7.48052 gallons.
- Liner sizing adds twice the average depth plus a material-specific overlap allowance (1 ft for vinyl and reinforced PVC) to both length and width.
- Fill water cost is estimated from the local rate you enter per 1,000 gallons and doesn’t include sewer fees, which some utilities charge on top.
- Above-ground and in-ground pools use the same volume formula — only the liner overlap and installation details differ.
Common questions
How many gallons is a 24 × 12 ft pool?
At a 5 ft average depth, a 24 × 12 ft pool holds about 10,772 gallons.
How do I calculate volume for a pool with a sloped floor?
Average the shallow and deep end depths — (shallow + deep) ÷ 2 — then use that average depth in the volume formula.
What size liner do I need for my pool?
Add twice your average depth plus a 1 ft overlap allowance to both the length and width of your pool’s dimensions.
How much does it cost to fill a pool?
Multiply your pool’s gallons by your water utility’s rate per 1,000 gallons — a 10,772-gallon pool costs roughly $43 at $4/1,000 gal.
How many gallons per cubic foot of water?
1 cubic foot of water equals 7.48052 gallons — the standard conversion for pool, pond, and tank volume calculations.
What's the difference between vinyl and PVC pool liner?
Standard vinyl liner (20-28 mil) suits most above and in-ground pools; reinforced PVC is thicker and more puncture- and UV-resistant for heavier-duty use.
How much overlap should pool liner have?
About 1 ft beyond the pool’s edge is standard, giving enough material to reach the bead track or coping for a secure fit.
Does pool volume include the liner or just the water?
Volume calculations measure the water the pool holds based on its interior dimensions — not the liner material itself.
How fast does a pool lose water to evaporation?
Roughly 1/4-1/2 inch of water level per day depending on climate — top off as needed rather than refilling fully.
How deep should an average pool be?
Most residential pools average 4-6 ft deep, often sloping from about 3 ft at the shallow end to 7-8 ft at the deep end.
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Project
| Shape | — |
| Dimensions | — |
| Depth | — |
Results
| Volume | — |
| Surface area | — |
| Liner size | — |
| Estimated total cost | — |
Notes
Estimate generated by materialcalculate.com. Confirm quantities with your supplier before ordering.