Pool Water Calculator
Planning a new pool, refilling after a drain, or budgeting a monthly water bill? This pool water calculator returns the total pool water volume in gallons and liters, the cost to fill from a municipal supply, how long it'll take from a garden hose, a chemical dosing reference for liquid chlorine, and a typical monthly evaporation top-up. Works for rectangle, round, oval, and kidney shapes. Covers above ground pool water calculator use cases and in-ground pools up to 200,000 gallons.
Pool Water Volume Formula
- Rectangle: Length x Width x Avg Depth x 7.48 = gallons
- Round: pi x Radius^2 x Avg Depth x 7.48
- Pool water calculator oval: pi x (Length/2) x (Width/2) x Avg Depth x 7.48
- Kidney: Length x Width x Avg Depth x 7.0 (irregular bottom coefficient)
Converting: 1 cubic foot = 7.48 US gallons = 28.32 liters. 1 gallon weighs 8.34 lbs.
Swimming Pool Water Calculator Reference Volumes
| Pool Size | Shape | Avg Depth | Volume |
|---|---|---|---|
| 16 x 32 ft | Rectangle | 5 ft | 19,150 gal |
| 18 x 36 ft | Rectangle | 5 ft | 24,250 gal |
| 20 x 40 ft | Rectangle | 5 ft | 29,900 gal |
| 24 ft | Round | 4.3 ft | 14,650 gal |
| 18 ft | Round | 4.3 ft | 8,250 gal |
| 15 x 30 ft | Oval | 4.3 ft | 11,380 gal |
| 12 x 24 ft | Oval | 4 ft | 6,770 gal |
| 16 x 32 ft | Kidney | 5 ft | 17,900 gal |
Above Ground Pool Water Calculator
An above ground pool water calculator uses the same math as an in-ground. Most above ground pools are round or oval with a consistent flat bottom, so the single-average-depth setting works fine. A 24 ft round above ground pool filled to 4.3 ft holds about 14,650 gallons. A 15 x 30 ft oval above ground pool holds about 11,380 gallons at the same depth. The fill cost from a garden hose at $4 per 1,000 gallons is about $46-60.
Pool Water Calculator Chemicals
Once you know your pool water volume in gallons, chemical dosing is straightforward. A pool water calculator chemicals reference:
- Liquid chlorine (10%): 10.5 oz per 10,000 gal raises free chlorine by 1 ppm
- Granular cal-hypo (65%): 1.55 oz per 10,000 gal per 1 ppm
- Muriatic acid (31.45%): 26 oz per 10,000 gal lowers pH by 0.2
- Soda ash (pH up): 6 oz per 10,000 gal raises pH by 0.2
- Baking soda (alkalinity up): 1.5 lb per 10,000 gal raises TA by 10 ppm
- Cyanuric acid (stabilizer): 13 oz per 10,000 gal raises CYA by 10 ppm
- Pool salt: 40 lb per 10,000 gal brings 0 ppm pool to ~3,200 ppm
Add chemicals in order: alkalinity first, pH second, cyanuric acid third, chlorine last. Wait at least 4 hours between doses.
Pool Water Calculator App vs Website
Looking for a pool water calculator app on your phone? Bookmark this page and pin it to your home screen; it works offline in any mobile browser. There is also a dedicated pool chemical calculator and a more detailed pool pump calculator for GPM and horsepower sizing. All three are free, no install required, and use the same formulas industry pool professionals use.
Swimming Pool Water Capacity Calculator Tips
A swimming pool water capacity calculator is only as accurate as your measurements. Two common mistakes:
- Measuring outside instead of inside the pool. Always measure the actual water dimensions, waterline to waterline, not the outside of the coping or deck. That overstates volume by 10-20%.
- Not averaging the depth properly. For pools with a shallow and deep end, average depth equals (shallow + deep) / 2, not the middle depth. A 3 ft shallow / 8 ft deep pool averages 5.5 ft, which matters because chemical doses scale linearly with volume.