Pool Volume Calculator
Every Chemical Dose Starts With This Number
Pool volume in gallons is the single figure that every other pool calculation depends on — chemical dosing, pump sizing, fill time, and heating cost all scale directly off of it. Yet most pool owners only have a rough estimate, often copied from a builder's spec sheet years ago. Because a pool's shape determines which geometric formula applies, this calculator handles rectangular, round, and oval pools separately rather than forcing one formula to approximate all three.
The Formulas
Round: Volume (gal) = π × r² × Avg Depth × 7.48
Oval: Volume (gal) = Length × Width × Avg Depth × 5.9
The constant 7.48 converts cubic feet to gallons (7.48052 gallons per cubic foot). The oval formula's 5.9 constant is the industry-standard shortcut equivalent to Length × Width × Avg Depth × π/4 × 7.48, accounting for the tapered elliptical shape.
Worked Examples by Shape
| Shape | Dimensions | Volume (gallons) | Volume (liters) |
|---|---|---|---|
| Rectangular | 32 ft × 16 ft, 5 ft avg depth | 19,150 gal | 72,491 L |
| Round | 24 ft diameter, 4.5 ft avg depth | 15,228 gal | 57,652 L |
| Oval | 40 ft × 20 ft, 5 ft avg depth | 23,600 gal | 89,336 L |
Average depth — not maximum depth — is what these formulas need. For a pool with a shallow and deep end, average the two depths (or measure at several points and average) before entering it.
Where This Calculation Matters
- Chemical dosing — chlorine, algaecide, and pH adjuster amounts all scale with gallons, so an inaccurate volume throws off every treatment calculation downstream.
- Pump and filter sizing — turnover rate calculations (how long it takes to circulate the entire pool once) require an accurate gallon figure as the starting point.
- Heating cost estimates — the energy needed to raise water temperature is directly proportional to the number of gallons being heated.
How to Use This Calculator
- Select your pool's shape — rectangular, round, or oval.
- For rectangular or oval pools, enter length, width, and average depth in feet.
- For round pools, enter diameter and average depth in feet.
- Select Calculate to see the volume in both gallons and liters.
Related Calculations
Once you have your volume, use the Pool Chemical Dosage Calculator to figure out treatment amounts, or the Pool Fill Time Calculator to estimate how long a fresh fill will take.