How to Calculate How Many Gallons Are in Your Pool
Start by measuring your pool’s overall dimensions, then plug them into the formula for your pool’s shape.
- Measure the length and width.
- Find the average depth — for sloped floors, add the shallow-end and deep-end depths, then divide by 2.
- Apply the formula for your pool’s shape (below), then multiply by 7.48 to convert cubic feet to gallons.
Formulas by Pool Shape
Rectangular Pools
Formula: Length × Width × Average Depth × 7.48
Example: 20 ft × 10 ft × 4 ft = 800 cu ft → 800 × 7.48 = ~5,984 gallons
Round Pools
Formula: (Diameter × Diameter ÷ 4) × 3.14 × Average Depth × 7.48
Measure the pool at its widest point for the diameter.
Example: 12 ft diameter × 4 ft deep = 452 cu ft → 452 × 7.48 = ~3,380 gallons
Oval Pools
Formula: (Length × Width ÷ 4) × 3.14 × Average Depth × 7.48
Measure the longest diameter (length) and the widest diameter (width).
Example: 40 ft × 20 ft × 6 ft deep = 3,768 cu ft → 3,768 × 7.48 = ~28,184 gallons
Frequently Asked Questions
What measurements do I need?
Measure the length, width, and average depth. For round pools, measure the widest diameter. For oval pools, measure both the longest and widest diameters. Compute cubic feet using the formula for your shape, then multiply by 7.48 to get gallons.
How do I find average depth if my pool floor is sloped?
Add the shallow-end depth and the deep-end depth, then divide by two. Use that average in your pool’s volume formula.
Why do I multiply by 7.48?
Because 1 cubic foot equals approximately 7.48 gallons. All the formulas above give volume in cubic feet first — multiplying by 7.48 converts that to gallons.
How accurate are these calculations?
They’re reliable estimates. Real pools can have minor irregularities that slightly affect true volume. Use the formulas to get close, then confirm with an online pool volume calculator or contact one of our representatives for a precise answer.
Note: Water levels drop daily due to evaporation, so you’ll need to top off your pool periodically to maintain proper levels.
Quick Reference
- Rectangular: L × W × Avg Depth × 7.48
- Round: (D × D ÷ 4) × 3.14 × Avg Depth × 7.48
- Oval: (L × W ÷ 4) × 3.14 × Avg Depth × 7.48
These are estimates — actual volume may vary slightly. When in doubt, use an online pool volume calculator to double-check your numbers.
Looking for pool services? Contact us here or fill out the free quote form below.
