Pool Volume Calculator
Free swimming pool volume calculator — capacity in gallons and litres for round, rectangular, oval, kidney or L-shape
How to Measure
- Measure from the water line, not the wall top
- Use feet and decimals (e.g., 25.5 not 25'6")
- For circles, measure across the widest point
- Depth measurements should be at deepest and shallowest points
Why Volume Matters
Knowing your pool's volume is essential for:
- • Adding the correct amount of chemicals
- • Determining pump and filter run times
- • Calculating heating costs
- • Ordering the right amount of water for fills
Common Pool Sizes
How We Calculate Pool Volume
Rectangle/Square Pools
Formula: Length × Width × Average Depth × 7.5
The 7.5 converts cubic feet to gallons (1 cubic foot = 7.48 gallons)
Round (Circle) Pool Volume Calculator
Formula: π × (Diameter ÷ 2)² × Average Depth × 7.5
The round pool volume calculator uses the radius (half the diameter) to find the circular area — measure across the widest point for diameter.
Oval Pools
Formula: π × (Length ÷ 2) × (Width ÷ 2) × Average Depth × 7.5
Similar to circles but using two different radii
Kidney Pool Volume Calculator
Estimate: 0.45 × (Width A + Width B) × Length × Average Depth × 7.48
The kidney pool volume calculator uses the industry-standard 0.45 approximation (±10%). Measure the widest lobe (A), narrow waist (B), end-to-end length — or enter the true surface area from your plans to skip the approximation.
Pro Tip: For variable depth pools, we calculate the average depth as (Shallow Depth + Deep Depth) ÷ 2. This gives you an accurate volume for chemical dosing and maintenance.
Common pool sizes (sanity-check your result)
Average water depth, not wall height. If your result is far off, re-measure the waterline.
| Shape & size | Avg depth | Gallons | Litres |
|---|---|---|---|
| 24 ft round | 4.5 ft | ~15,200 | ~57,500 |
| 16 × 32 ft rectangle | 5 ft | ~19,100 | ~72,300 |
| 18 × 36 ft rectangle | 5 ft | ~24,200 | ~91,600 |
| 30 × 15 ft oval | 5 ft | ~13,200 | ~50,000 |
Pool volume FAQs
Should I use average depth or deep-end depth?
Always average: (shallow + deep) ÷ 2. Using deep-end only overdoses every chemical by up to 40%.
How do I convert pool gallons to litres?
Multiply gallons × 3.78541 = litres. US labels dose by gallons; AU/UK labels by litres. This pool volume calculator shows both — no manual conversion needed.
How does the round pool volume calculator work?
Measure the diameter across the widest point, halve it for the radius, then apply 3.14 × radius² × depth × 7.48. A 24 ft round pool at 4.5 ft holds about 15,200 gallons (57,500 litres).
How does the kidney pool volume calculator work?
Use the 0.45 × (Width A + Width B) × Length method above, or enter the true surface area from your plans. Kidney and freeform pools are estimates (±10%) — round up and dose in stages.
Why 7.48 vs 7.5?
1 ft³ = 7.48052 gal. Charts round to 7.5 for mental math — we use 7.48052 for accuracy.