01
The purpose
What does this calculator estimate?
Instant volume for circular pools in gallons, liters & cubic feet — just enter your diameter and depth.
Volume & Capacity · A2
Round Pool Volume Calculator
Instant volume for circular pools in gallons, liters & cubic feet — just enter your diameter and depth.
Measure the inputsMost round above-ground pools have a flat floor — enter the same value for shallow and deep depth.
Read the full resultMeasure the diameter at the waterline, not across the top rail, which overstates the size.
Check the boundaryA round pool holds about 21% less water than a square pool of the same width — the corners are missing.
Useful forVolume & CapacityPlanningComparisonVerification
Live calculation
Pool dimensions
✓ Checked May 2026
Enter your pool diameter and depths and we'll calculate instantly.
Calculated result
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Enter the required values to calculate.
Enter the known values. Let the engine handle the calculation.
✓ Formula checked↻ Live result○ No account needed
Planning estimate only. Confirm product labels, equipment specifications, qualified-professional advice and local requirements before acting.
The result, explained
Use the Round Pool Volume Calculator result with context.
Instant volume for circular pools in gallons, liters & cubic feet — just enter your diameter and depth.
02
The tool
What information does it use?
- Diameter: Measure straight across the widest point of the water surface.
- Shallow end depth: Most round above-ground pools have one uniform depth — enter it in both fields.
- Deep end depth: enter a measured or verified value
- Hose / fill rate: Garden hose: 5–17 GPM depending on pressure & diameter.
- Local water rate: Average US municipal water: $0.004–0.008 / gallon.
03
The method
How to use this calculator
- DiameterMeasure straight across the widest point of the water surface.
- Shallow end depthMost round above-ground pools have one uniform depth — enter it in both fields.
- Deep end depthEnter the value you can verify.
- Hose / fill rateGarden hose: 5–17 GPM depending on pressure & diameter.
- Local water rateAverage US municipal water: $0.004–0.008 / gallon.
04
The relationship
The formula in plain English
Volume = π × Radius² × Avg. Depth × 7.48
Radius = Diameter ÷ 2 | Avg. depth = (Shallow + Deep) ÷ 2 | ×7.48 converts ft³ → US gallons05
Worked through
A worked example: 24 ft round above-ground pool, 4 ft deep
- Radius = 24 ÷ 2 = 12 ft
- Surface area = π × 12² = 452 ft²
- Volume = 452 × 4 × 7.48 = 13,538 gallons
| Diameter | Surface area | Volume (US gal) | Volume (litres) | Water weight | Fill time @ 9 GPM |
|---|---|---|---|---|---|
| 12 ft | 113 ft² | 3,383 | 12,807 | 14.1 tons | ~6 hrs |
| 15 ft | 177 ft² | 5,288 | 20,019 | 22.0 tons | ~10 hrs |
| 18 ft | 254 ft² | 7,613 | 28,820 | 31.7 tons | ~14 hrs |
| 21 ft | 346 ft² | 10,362 | 39,224 | 43.2 tons | ~19 hrs |
| 24 ft | 452 ft² | 13,538 | 51,245 | 56.4 tons | ~25 hrs |
| 27 ft | 573 ft² | 17,128 | 64,830 | 71.4 tons | ~32 hrs |
| 30 ft | 707 ft² | 21,145 | 80,036 | 88.1 tons | ~39 hrs |
06
Why it matters
How the result supports the next decision
Most round above-ground pools have a flat floor — enter the same value for shallow and deep depth.
Measure the diameter at the waterline, not across the top rail, which overstates the size.
07
Good inputs
Improve the estimate before relying on it
- Most round above-ground pools have a flat floor — enter the same value for shallow and deep depth.
- Measure the diameter at the waterline, not across the top rail, which overstates the size.
- A round pool holds about 21% less water than a square pool of the same width — the corners are missing.
- For soft-sided and Intex-style pools, fill to the recommended line (usually 80–90% of wall height), not the top.
- Re-check diameter on resin and steel-wall pools after installation — they can flex outward 1–2 inches once filled.
08
The boundary
How to interpret the result
Measurements, equipment specifications, site conditions and local requirements can change the practical result.
The engine reports invalid inputs and safety warnings beside the result. Resolve those messages before using the estimate.
09
Before acting
What should override this estimate?
- Measured site conditions and current test results
- Product labels and manufacturer specifications
- Qualified-professional advice and applicable local codes
10
Common questions
Frequently asked questions
How do I measure the diameter of a round pool?
Stretch a tape measure straight across the center of the pool at the waterline, from inside wall to inside wall. If you can't reach the center, measure the radius from the center to one edge and double it. Always measure the water surface, not the outer frame.
Why does a round pool hold less water than a square one?
A circle inscribed in a square fills only about 78.5% of the square's area. So a 24 ft round pool holds roughly 21% less water than a 24 × 24 ft square pool of the same depth. This is why you can't reuse square-pool volume figures for round pools.
How many gallons is a 24 ft round pool?
A 24 ft diameter round pool at 4 ft average depth holds approximately 13,538 US gallons. At 4.5 ft it holds about 15,230 gallons. Use the calculator with your actual depth for an exact figure.
Do I use the same depth for shallow and deep on an above-ground pool?
Yes. Almost all round above-ground pools have a single uniform depth, so enter that same number in both the shallow and deep fields. In-ground round pools occasionally slope — only then should the two values differ.
How long does it take to fill a round pool?
Divide the volume by your fill rate. A 24 ft round pool at 13,500 gallons takes about 25 hours with a 9 GPM garden hose, or roughly 12 hours with two hoses running together.
How many gallons is a 15 ft round pool?
A 15 ft round pool at 4 ft average depth holds approximately 5,288 US gallons (20,019 litres) — a common size for smaller above-ground pools.
How many gallons is a 27 ft round pool?
A 27 ft round pool at 4 ft average depth holds approximately 17,128 US gallons. At 52-inch wall height filled to 4 ft of water, this is one of the largest standard above-ground sizes.
Is pool diameter measured inside or outside the wall?
Always measure the inside diameter at the waterline. The outside frame or top rail can add several inches, which would overstate your volume and throw off chemical dosing.
Primary sources
Use the result with current guidance.
These official references support safe planning context. Product labels, local requirements and qualified-professional advice take priority over a general calculator estimate.