01
The purpose
What does this calculator estimate?
Instant volume in gallons, liters & cubic feet — plus water weight and fill-time estimates.
Volume & Capacity · A1
Rectangular Pool Volume Calculator
Instant volume in gallons, liters & cubic feet — plus water weight and fill-time estimates.
Measure the inputsFor sloped floors, always use the average of shallow and deep ends — never just one depth.
Read the full resultOver-estimate by 3–5%: pumps, heaters, and chemical dosing all depend on accurate volume.
Check the boundaryMeasure interior dimensions (water surface) not outer shell dimensions.
Useful forVolume & CapacityPlanningComparisonVerification
Live calculation
Pool dimensions
✓ Checked May 2026
Enter your pool measurements and we'll calculate instantly.
Calculated result
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Enter the four required pool dimensions 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 Rectangular Pool Volume Calculator result with context.
Instant volume in gallons, liters & cubic feet — plus water weight and fill-time estimates.
02
The tool
What information does it use?
- Length: enter a measured or verified value
- Width: enter a measured or verified value
- 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
- LengthEnter the value you can verify.
- WidthEnter the value you can verify.
- 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 = Length × Width × Avg. Depth × 7.48
Avg. depth = (Shallow + Deep) ÷ 2 | ×7.48 converts ft³ → US gallons05
Worked through
A worked example: 16 × 32 ft pool, 3 ft shallow / 8 ft deep
- Avg depth = (3 + 8) ÷ 2 = 5.5 ft
- Volume = 32 × 16 × 5.5 × 7.48 = 21,065 gallons
| Pool size | Surface area | Volume (US gal) | Volume (litres) | Water weight | Fill time @ 9 GPM |
|---|---|---|---|---|---|
| 12 × 24 ft | 288 ft² | 10,771 | 40,769 | 44.9 tons | ~20 hrs |
| 14 × 28 ft | 392 ft² | 14,660 | 55,480 | 61.1 tons | ~27 hrs |
| 16 × 32 ft | 512 ft² | 19,149 | 72,464 | 79.8 tons | ~35 hrs |
| 18 × 36 ft | 648 ft² | 24,221 | 91,677 | 101.0 tons | ~45 hrs |
| 20 × 40 ft | 800 ft² | 29,922 | 113,270 | 124.7 tons | ~55 hrs |
| 20 × 50 ft | 1,000 ft² | 37,403 | 141,588 | 155.9 tons | ~69 hrs |
| 25 × 50 ft | 1,250 ft² | 46,753 | 176,976 | 194.9 tons | ~87 hrs |
06
Why it matters
How the result supports the next decision
For sloped floors, always use the average of shallow and deep ends — never just one depth.
Over-estimate by 3–5%: pumps, heaters, and chemical dosing all depend on accurate volume.
07
Good inputs
Improve the estimate before relying on it
- For sloped floors, always use the average of shallow and deep ends — never just one depth.
- Over-estimate by 3–5%: pumps, heaters, and chemical dosing all depend on accurate volume.
- Measure interior dimensions (water surface) not outer shell dimensions.
- Salt pools need exact volume for cell calibration — re-measure after any renovation.
- Water weight matters for structural design: a 20,000-gal pool adds ~83 tons of load.
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 is accurate pool volume important?
Pool volume is the foundation of every chemical calculation. An error of 20% in your volume estimate means every dose of chlorine, acid, or calcium you add is off by 20% — which throws the entire water balance out.
How do I convert gallons to litres?
Multiply US gallons by 3.78541. For example, 20,000 gal × 3.785 = 75,708 liters. Our calculator shows this automatically in the results panel.
What if my pool has an irregular floor?
For multiple depth transitions, break the pool into zones, calculate each zone's volume separately, and sum them. Use our Freeform estimator for non-standard floors.
How long does it take to fill a pool?
Fill time = Volume ÷ Fill rate. A standard 3/4-inch garden hose runs at about 9 GPM. A 20,000-gallon pool takes roughly 37 hours continuously.
Does water temperature affect volume?
Yes, but only slightly. Water expands about 0.0115% per degree F. Heating a 20,000-gal pool from 60F to 85F expands it by about 58 gallons — negligible for most purposes.
How many gallons is a 12×24 pool?
A 12×24 ft pool with an average depth of 5 ft holds approximately 10,771 US gallons (40,769 litres).
How many gallons is a 16×32 pool?
A 16×32 ft pool at 5 ft average depth holds approximately 19,149 US gallons — one of the most common residential sizes in North America.
How do I measure my pool's depth accurately?
Use a fibreglass measuring rod or a weighted string. Measure at the deepest and shallowest points of the water — not from the coping. For sloped floors, take readings every 2 ft and average them.
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.