Pool Volume and Chemical Dosage Calculator
Enter your pool dimensions and get its volume in gallons, plus how much of each chemical that volume actually takes.
To find your pool volume, multiply the surface area in square feet by the average depth in feet, then by 7.48 gallons per cubic foot. A 16 by 32 foot rectangle with a 3 foot shallow end and an 8 foot deep end averages 5.5 feet and holds about 21,000 gallons. Volume is the number every chemical dose depends on, so it is worth getting right once.
Pool shape
Your pool holds about
21,064 gallons
Average depth 5.5 ft. Rounded, and accurate enough for dosing. A pool with steps, benches, or a tapered bottom holds slightly less.
What to Add to This Pool
Scaled to 21,064 gallons. Add one product at a time, run the pump at least 20 minutes, then retest before adding anything else.
| To do this | Use | Amount |
|---|---|---|
| Raise free chlorine by 1 ppm | Liquid chlorine (12.5% sodium hypochlorite) | 21 fl oz |
| Raise free chlorine by 1 ppm | Cal-hypo shock (73% calcium hypochlorite) | 4 oz |
| Shock to 10 ppm | Liquid chlorine (12.5%) | 1.7 gal (215 fl oz) |
| Raise total alkalinity by 10 ppm | Baking soda (sodium bicarbonate) | 3.2 lb |
| Raise pH by 0.2 | Soda ash (sodium carbonate) | 15 oz |
| Raise stabilizer (CYA) by 10 ppm | Cyanuric acid | 2.1 lb |
| Raise salt by 100 ppm | Pool-grade salt | 17 lb |
Dosing charts and derivations as of August 2026. These are starting points, not prescriptions. Water that is far out of range should be corrected over several days rather than in one afternoon.
Where Your Numbers Should Sit
| Reading | Target | Note |
|---|---|---|
| Free chlorine | 1 to 3 ppm | Higher if stabilizer is high. |
| pH | 7.2 to 7.6 | The single most important number. |
| Total alkalinity | 80 to 120 ppm | Balance this before chasing pH. |
| Stabilizer (CYA) | 30 to 50 ppm | Only comes down by draining water. |
| Salt (salt pools) | 2,700 to 3,400 ppm | Check your cell manual. |
How to Measure Your Pool
Measure at the waterline, not the outside of the coping, and measure both depths. The shallow and deep ends matter more than people expect: the same 16 by 32 rectangle holds about 21,000 gallons with a 3 to 8 foot slope and about 15,300 gallons with a flat 4 foot bottom. That difference is roughly a third of your chemical dose.
For a freeform or kidney shape, measure the longest length and the average width, then use the oval setting. It will be within a few percent, which is close enough for dosing. Steps, benches, and tanning ledges all displace water, so treat the result as a slight overestimate.
Fix Things in the Right Order
Total alkalinity first, then pH, then chlorine. Alkalinity buffers pH, so adjusting pH while alkalinity sits outside 80 to 120 ppm means watching it drift straight back. Stabilizer comes last and only if a test says it is low, because the only way to bring it down again is to drain water and replace it.
Add one product at a time with the pump running, give it at least 20 minutes to circulate, and retest before the next dose. Water that is badly out of range is a several-day project. Trying to fix everything in one afternoon is how people overshoot and end up chasing the numbers in the other direction for a week.
When to Stop and Call Someone
Cloudy water that will not clear after a shock and a full filter cycle, chlorine that reads zero no matter how much you add, or a persistent green tint usually means something mechanical is wrong rather than something chemical. Circulation, filter condition, and a high stabilizer level are the usual culprits, and none of them are solved by adding more chemicals.
Keep Reading
Pool Volume and Chemistry Questions
About 21,000 gallons with a shallow end of 3 feet and a deep end of 8 feet, which averages 5.5 feet deep. A shallower 16x32 with a flat 4 foot bottom holds closer to 15,300 gallons. Depth changes the answer more than most people expect, so measure both ends.
Alkalinity first, always. Total alkalinity buffers pH, so adjusting pH while alkalinity sits outside 80 to 120 ppm means the pH drifts right back. Get alkalinity in range, let the water circulate, retest, and then adjust pH if it is still off.
About 10 fluid ounces of 12.5% liquid chlorine per 10,000 gallons. That works out from the chemistry: 12.5% is 125,000 ppm, so a full gallon in 10,000 gallons of water raises free chlorine by roughly 12.5 ppm.
No. Never mix pool chemicals with each other, and never combine chlorine and acid in any form, including in a bucket or a feeder. Add one product, run the pump for at least 20 minutes, and retest before adding anything else. Add chemicals to water, never water to chemicals.