01
The purpose
What does this calculator estimate?
Estimate the volume of a curved kidney pool in gallons, liters & cubic feet using the industry-standard method.
Volume & Capacity · A4
Kidney-Shaped Pool Volume Calculator
Estimate the volume of a curved kidney pool in gallons, liters & cubic feet using the industry-standard method.
Measure the inputsMeasure the two widths at the widest and narrowest points, and the length end to end through the curve.
Read the full resultThe 0.45 constant is an industry approximation — expect the result to be within about 5% of the true volume.
Check the boundaryIf your pool has a pronounced waist or extra lobe, take a third width measurement and average the widths for a closer estimate.
Useful forVolume & CapacityPlanningComparisonVerification
Live calculation
Pool dimensions
✓ Checked May 2026
Enter the overall length and the two widths (wide end and narrow end).
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 Kidney-Shaped Pool Volume Calculator result with context.
Estimate the volume of a curved kidney pool in gallons, liters & cubic feet using the industry-standard method.
02
The tool
What information does it use?
- Length: Longest straight-line distance from end to end.
- Width — wide end: The widest part of the kidney, usually the lobe end.
- Width — narrow end: The narrower waist or opposite end.
- Shallow end depth: enter a measured or verified value
- 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
- LengthLongest straight-line distance from end to end.
- Width — wide endThe widest part of the kidney, usually the lobe end.
- Width — narrow endThe narrower waist or opposite end.
- Shallow end depthEnter the value you can verify.
- 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 = 0.45 × (Width₁ + Width₂) × Length × Avg. Depth × 7.48
0.45 is the pool-industry constant for kidney curves | ×7.48 converts ft³ → US gallons05
Worked through
A worked example: 32 ft kidney pool, widths 16 ft & 10 ft, 3.5 ft shallow / 6.5 ft deep
- Avg depth = (3.5 + 6.5) ÷ 2 = 5 ft
- Surface area = 0.45 × (16 + 10) × 32 = 374 ft²
- Volume = 374 × 5 × 7.48 = 14,003 gallons
| Length | Widths (W₁ / W₂) | Surface area | Volume (US gal) | Water weight | Fill time @ 9 GPM |
|---|---|---|---|---|---|
| 24 ft | 12 / 8 ft | 216 ft² | 8,078 | 33.7 tons | ~15 hrs |
| 28 ft | 14 / 9 ft | 290 ft² | 10,839 | 45.2 tons | ~20 hrs |
| 32 ft | 16 / 10 ft | 374 ft² | 14,003 | 58.4 tons | ~26 hrs |
| 36 ft | 18 / 11 ft | 470 ft² | 17,572 | 73.3 tons | ~33 hrs |
| 40 ft | 20 / 12 ft | 576 ft² | 21,542 | 89.8 tons | ~40 hrs |
06
Why it matters
How the result supports the next decision
Measure the two widths at the widest and narrowest points, and the length end to end through the curve.
The 0.45 constant is an industry approximation — expect the result to be within about 5% of the true volume.
07
Good inputs
Improve the estimate before relying on it
- Measure the two widths at the widest and narrowest points, and the length end to end through the curve.
- The 0.45 constant is an industry approximation — expect the result to be within about 5% of the true volume.
- If your pool has a pronounced waist or extra lobe, take a third width measurement and average the widths for a closer estimate.
- For chemical dosing, round the estimate up slightly rather than down — under-dosing leaves the water unprotected.
- When precision matters (salt cell sizing, heater specs), confirm against the original pool plan if you have it.
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
Why does the kidney formula use a 0.45 constant?
A kidney shape is too irregular for a clean geometric formula, so the pool industry uses an empirical constant of 0.45 applied to the average of the two widths times the length. It gives a reliable estimate — typically within 5% of the true volume — without needing to map the exact curve.
Where do I measure the two widths on a kidney pool?
Measure the first width at the widest point — usually the larger lobe — and the second at the narrowest point, often the waist where the kidney curves inward. The length is the longest straight-line distance from one end to the other.
How accurate is a kidney pool volume estimate?
The 0.45 method is accurate to roughly ±5% for typical kidney shapes. Pools with an exaggerated curve or a second lobe may vary more. For most purposes — chemical dosing, fill time, heater sizing — that margin is well within acceptable tolerance.
How many gallons is a typical kidney pool?
A common 32 ft kidney pool with widths of 16 ft and 10 ft at 5 ft average depth holds approximately 14,000 US gallons. Smaller backyard kidneys often fall between 10,000 and 15,000 gallons.
Should I round my kidney volume estimate up or down?
Round up. Because this is an approximation, slightly overestimating ensures you don't under-dose chemicals or undersize equipment. A pool that's treated as marginally larger than reality stays safely balanced; the reverse can leave it under-protected.
How do you calculate the volume of a kidney pool?
Multiply 0.45 by the sum of the two widths, then by the length and the average depth, then by 7.48 to convert to US gallons. The 0.45 constant accounts for the curved kidney shape.
How many gallons is a 28 ft kidney pool?
A 28 ft kidney pool with widths of 14 ft and 9 ft at 5 ft average depth holds approximately 10,839 US gallons (41,029 litres).
Is a kidney pool volume exact?
No — it's an estimate within about 5% because the kidney shape doesn't fit a precise formula. The industry 0.45 constant gives a dependable working figure for dosing and equipment sizing.
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.