# Pool Water Calculator

> Pool Water Calculator (https://www.poolwatercalculator.com) publishes free, browser-based swimming pool calculators and guides: pool volume in gallons and liters for any shape, chemical dosing (chlorine, pH, alkalinity, calcium hardness, cyanuric acid, shock, saturation index), salt for saltwater pools, and inground pool cost estimates. Every formula and constant is documented at https://www.poolwatercalculator.com/methodology/. Results are estimates for residential pools.

Key facts: 1 cubic foot = 7.48 US gallons. Rectangle volume = length × width × average depth × 7.48; round = diameter² × average depth × 5.9. Raising free chlorine 1 ppm in 10,000 gallons takes about 12.8 fl oz of 10% liquid chlorine. Raising 10,000 gallons from 0 to 3,200 ppm salt takes about 267 lb of salt.

## Pool Volume

- [Pool Volume Calculator](https://www.poolwatercalculator.com/pool-volume-calculator/): Pool volume in US gallons is surface area × average depth × 7.48. For a rectangle, multiply length × width × average depth × 7.48; for a round pool, diameter² × average depth × 5.9; for an oval, length × width × average depth × 5.9. Average depth is (shallow end + deep end) ÷ 2. A 16 × 32 ft pool averaging 5.5 ft deep holds about 21,065 gallons (79,740 liters).
- [Rectangle Pool Volume Calculator](https://www.poolwatercalculator.com/pool-volume-calculator/rectangle-pool/): A rectangular pool holds length × width × average depth × 7.48 US gallons, with all measurements in feet and average depth = (shallow end + deep end) ÷ 2. An 18 × 36 ft pool that runs from 3.5 ft to 8 ft deep averages 5.75 ft and holds about 27,872 gallons (105,509 liters). For hopper-bottom diving pools, average several depth readings instead.
- [Round Pool Gallons Calculator](https://www.poolwatercalculator.com/pool-volume-calculator/round-pool/): A round pool holds diameter² × average depth × 5.9 US gallons, with measurements in feet. The 5.9 is π ÷ 4 × 7.48 (exactly 5.875). A 24 ft round pool with 4 ft of water holds about 13,536 gallons (51,241 liters); at 4.5 ft it holds about 15,228 gallons. Measure diameter inside the wall, through the center.
- [Oval Pool Volume Calculator](https://www.poolwatercalculator.com/pool-volume-calculator/oval-pool/): An oval pool holds length × width × average depth × 5.9 US gallons, with measurements in feet. The 5.9 (exactly 5.875) is π ÷ 4 × 7.48, the ellipse area times gallons per cubic foot. A 15 × 30 ft oval with 4 ft of water holds about 10,575 gallons (40,032 liters). Ovals with straight sides hold more and need the split method.
- [Kidney Pool Volume Calculator](https://www.poolwatercalculator.com/pool-volume-calculator/kidney-pool/): A kidney-shaped pool holds about 0.45 × (A + B) × length × average depth × 7.48 US gallons, where A and B are the widths of the two lobes in feet. A kidney pool 32 ft long with lobes 10 ft and 16 ft wide, averaging 4.5 ft deep, holds about 12,603 gallons (47,708 liters). Freeform results are estimates, typically good enough for dosing.
- [Above Ground Pool Gallons Calculator](https://www.poolwatercalculator.com/pool-volume-calculator/above-ground-pool/): An above-ground pool's gallons are based on its water depth, not its wall height. Water usually sits about 6 inches below the top of the wall, so a 54 in wall holds about 48 in of water. A 24 ft round pool with 48 in of water holds about 13,536 gallons (51,241 liters); a 15 × 30 ft oval at 48 in holds about 10,575 gallons.
- [How Long to Fill a Pool Calculator](https://www.poolwatercalculator.com/pool-volume-calculator/pool-fill-time-calculator/): Fill time in hours = pool gallons ÷ hose flow in gallons per minute (GPM) ÷ 60. A typical 5/8 in garden hose delivers roughly 9–17 GPM depending on water pressure. At 10 GPM, a 21,065-gallon pool takes about 35 hours and a 13,536-gallon pool about 22.6 hours. Time how many seconds your hose takes to fill a 5-gallon bucket: GPM = 300 ÷ seconds.

## Pool Chemicals

- [Pool Chemical Calculator](https://www.poolwatercalculator.com/pool-chemical-calculator/): A pool chemical calculator compares your test results with target ranges and converts each gap into a product dose for your pool's volume. Balance in this order: total alkalinity (60–120 ppm), pH (7.2–7.8), calcium hardness (200–400 ppm), stabilizer (30–50 ppm, 60–80 for salt), then free chlorine at about 11.5% of your CYA. Retest between steps, and never mix chemicals.
- [Pool Chlorine Calculator](https://www.poolwatercalculator.com/pool-chemical-calculator/chlorine-calculator/): To raise free chlorine by 1 ppm in 10,000 gallons you need about 12.8 fl oz of 10% liquid chlorine, 10.2 fl oz of 12.5% liquid chlorine, 21.3 fl oz of 6% bleach, 2.05 oz of 65% cal-hypo, 2.4 oz of 56% dichlor or 1.5 oz of 90% trichlor. Multiply by the ppm increase you need and by your gallons ÷ 10,000.
- [Pool pH Calculator](https://www.poolwatercalculator.com/pool-chemical-calculator/ph-calculator/): To lower a 15,000-gallon pool from pH 7.9 to 7.5 with TA 90 ppm and CYA 40 ppm, you need about 17.7 fl oz of 31.45% muriatic acid. The same change takes about 13.2 fl oz at TA 60 and 22.1 fl oz at TA 120, because alkalinity and stabilizer resist pH change. Add half, circulate 30 minutes, retest, then finish. Aim for pH 7.4–7.6.
- [Pool Alkalinity Calculator](https://www.poolwatercalculator.com/pool-chemical-calculator/alkalinity-calculator/): About 1.4 lb of baking soda raises total alkalinity by 10 ppm in 10,000 gallons. A 20,000-gallon pool going from 60 to 90 ppm needs about 8.4 lb. To lower TA, add muriatic acid to bring pH to about 7.2, then aerate to raise pH without raising TA, and repeat; about 25.6 fl oz of 31.45% acid removes 10 ppm per 10,000 gallons. Most pools target 60–120 ppm.
- [Pool Calcium Hardness Calculator](https://www.poolwatercalculator.com/pool-chemical-calculator/calcium-hardness-calculator/): About 1.2 lb of 77–80% calcium chloride, or about 1.0 lb of 94–97% anhydrous calcium chloride, raises calcium hardness by 10 ppm in 10,000 gallons. Lowering CH means replacing water: share to replace = (current − target) ÷ (current − fill water hardness). Most pools target 200–400 ppm; plaster pools often run 250–450 ppm.
- [Cyanuric Acid Calculator](https://www.poolwatercalculator.com/pool-chemical-calculator/cyanuric-acid-calculator/): To raise cyanuric acid (CYA) by 10 ppm, add about 13.4 oz of stabilizer per 10,000 gallons. Most chlorine pools run 30–50 ppm CYA and salt pools 60–80 ppm. CYA does not break down or get filtered out, so the only practical way to lower it is to drain and refill: the share to replace is 1 − target ÷ current (90 → 50 ppm means replacing about 44%).
- [Pool Shock Calculator](https://www.poolwatercalculator.com/pool-chemical-calculator/shock-calculator/): Shock level is about 40% of your cyanuric acid (CYA) reading: 16 ppm free chlorine at 40 ppm CYA, 24 ppm at 60 ppm, 32 ppm at 80 ppm. Raising a 10,000-gallon pool by 1 ppm takes about 12.8 fl oz of 10% liquid chlorine or 2.05 oz of 65% cal-hypo. Hold the shock level until combined chlorine is 0.5 ppm or less, the water is clear, and overnight chlorine loss is 1 ppm or less.
- [Pool Saturation Index Calculator](https://www.poolwatercalculator.com/pool-chemical-calculator/saturation-index-calculator/): The saturation index (LSI or CSI) is pH + temperature factor + calcium factor + alkalinity factor − 12.1 (12.2 for salt pools). A result between −0.3 and +0.3 is balanced. Below −0.3 the water is corrosive and can etch plaster and attack metal; above +0.3 it tends to deposit calcium scale on tile, heaters and salt cells. Example: pH 7.5, 82°F, 300 ppm calcium, 90 ppm TA, 40 ppm CYA gives +0.04.
- [Chlorine CYA Chart](https://www.poolwatercalculator.com/pool-chemical-calculator/chlorine-cya-chart/): On a chlorine CYA chart, free chlorine scales with stabilizer: minimum FC is about 7.5% of CYA, the daily target is about 11.5% of CYA, and the shock level is about 40% of CYA. At 40 ppm CYA that means a 3 ppm minimum, a 4.6–6.6 ppm target and 16 ppm to shock. At 70 ppm CYA, typical of salt pools, it is 5.3, 8.1–10.1 and 28 ppm.

## Pool Salt

- [Pool Salt Calculator](https://www.poolwatercalculator.com/pool-salt-calculator/): Pounds of salt = (target ppm − current ppm) × gallons × 8.34 ÷ 1,000,000. About 8.3 lb raises 10,000 gallons by 100 ppm, and a new 10,000-gallon pool needs about 267 lb (6.7 forty-pound bags) to reach 3,200 ppm. Use the target in your salt chlorinator's manual; many cells call for roughly 2,700–3,400 ppm, often with about 3,200 ppm as ideal. Add about two-thirds, circulate 24 hours, retest, then add the rest.
- [How to Lower Salt in a Pool](https://www.poolwatercalculator.com/pool-salt-calculator/lower-salt-level/): To lower salt in a pool, drain part of the water and refill with fresh water; no chemical removes salt. The share to replace is 1 − target ÷ current. Going from 4,200 to 3,200 ppm means replacing about 24% of the water, roughly 4,760 gallons in a 20,000-gallon pool. Drain in stages, circulate for a day after each refill, and retest before draining more.
- [Salt Chlorinator Size Calculator](https://www.poolwatercalculator.com/pool-salt-calculator/salt-chlorinator-sizing/): A salt cell must replace your pool's daily chlorine loss: pounds per day = ppm lost per day × gallons × 8.34 ÷ 1,000,000. A 20,000-gallon pool losing 3 ppm a day needs 0.5 lb of chlorine daily. Common advice is to buy a cell rated for 1.5–2 times your pool volume (30,000–40,000 gallons here). Run time at 100% output = daily need ÷ cell output × 24 hours, so a 1.4 lb/day cell needs about 8.6 hours.

## Pool Cost

- [Inground Pool Cost Calculator](https://www.poolwatercalculator.com/inground-pool-cost/): A new inground pool typically costs $25,000 to $100,000 installed, according to HomeGuide, and HomeAdvisor reports most homeowners spend around $65,909. Vinyl liner pools are cheapest upfront ($25,000–$70,000 across HomeGuide, Fixr and This Old House), fiberglass runs $45,000–$100,000, and concrete (gunite or shotcrete) runs $50,000–$120,000. Fences, decking, heaters and covers are usually extra; HomeGuide puts decking alone at $5,000–$20,000.
- [Concrete Pool Cost](https://www.poolwatercalculator.com/inground-pool-cost/concrete-pool-cost/): A concrete (gunite or shotcrete) inground pool costs about $50,000 to $120,000 installed, or $165 to $300 per square foot, according to HomeGuide. Fixr's national average is $60,000 for a 12 × 24 ft shotcrete pool with tile and basic equipment. Plan on resurfacing every 7 to 15 years at roughly $6,000 to $15,000, which makes concrete the most expensive pool type to own over time.
- [Fiberglass Pool Cost](https://www.poolwatercalculator.com/inground-pool-cost/fiberglass-pool-cost/): A fiberglass inground pool costs about $45,000 to $100,000 installed, according to HomeGuide, and Fixr reports a $70,000 national average for a 15 × 30 ft pool with concrete deck, filter, heater and pump. Installation can finish in as little as two to four weeks (HomeAdvisor). Fiberglass uses the fewest chemicals of the three inground types, about $175 a year by HomeGuide's estimate, and lasts 25 to 30 years.
- [Vinyl Liner Pool Cost](https://www.poolwatercalculator.com/inground-pool-cost/vinyl-liner-pool-cost/): A vinyl liner inground pool costs about $25,000 to $65,000 installed, according to HomeGuide, and Fixr's national average is $45,000 for a 12 × 24 ft pool with steps, heater, filter and concrete deck. Expect to replace the liner every 5 to 12 years depending on the source, at $3,000 to $7,500 installed by HomeGuide's figures, so vinyl's upfront savings shrink over time.
- [Pool Maintenance Cost Calculator](https://www.poolwatercalculator.com/inground-pool-cost/pool-maintenance-cost/): Typical pool maintenance cost is $960 to $1,800 a year, with most owners spending about $1,400, according to HomeGuide. All-in ownership, including chemicals, electricity, water, repairs and opening and closing, runs $3,000 to $6,000 a year. Your own number depends mainly on how many months the pool is open, how much power the pump draws, and whether you pay for weekly service.

## Pool Water

- [Pool Water Care: Safe, Clear and Balanced](https://www.poolwatercalculator.com/pool-water/): Safe, clear pool water needs four things: free chlorine kept above a minimum set by your stabilizer (about 7.5% of CYA, so 3 ppm at 40 ppm CYA), pH between 7.2 and 7.8, a filter and pump that turn the water over daily, and balanced alkalinity and calcium. Test chlorine and pH several times a week, brush and skim weekly, and adjust in small steps.
- [Ideal Pool Water Chemistry Levels](https://www.poolwatercalculator.com/pool-water/pool-water-chemistry-levels/): Ideal pool water chemistry levels: free chlorine at least 7.5% of your CYA (3 ppm at 40 ppm CYA) with a target near 11.5% of CYA; combined chlorine 0.5 ppm or less; pH 7.2–7.8; total alkalinity 60–120 ppm; calcium hardness 200–400 ppm (250–450 for plaster); cyanuric acid 30–50 ppm, or 60–80 ppm in salt pools; and salt at your chlorinator's specified level, often around 3,200 ppm.
- [How to Test Pool Water Accurately](https://www.poolwatercalculator.com/pool-water/how-to-test-pool-water/): To test pool water, fill a clean bottle at elbow depth (about 18 in, 45 cm) away from return jets, then test right away. A FAS-DPD drop kit is the most reliable home test for free and combined chlorine; strips are fine for quick checks but less accurate. Test free chlorine and pH every day or two in season, and alkalinity, calcium and CYA every one to four weeks.
- [How to Fix Green Pool Water](https://www.poolwatercalculator.com/pool-water/green-pool-water/): To fix green pool water, test free chlorine, pH and cyanuric acid, brush the whole pool, then raise free chlorine to about 40% of your CYA (16 ppm at 40 ppm CYA) and hold it there with testing and top-ups several times a day. Run the filter around the clock and clean it as pressure rises. You are done when combined chlorine is 0.5 ppm or less, the water is clear, and chlorine drops 1 ppm or less overnight.
- [How to Clear Cloudy Pool Water](https://www.poolwatercalculator.com/pool-water/cloudy-pool-water/): Cloudy pool water is most often caused by free chlorine too low for your CYA, which lets early algae grow. Other causes are high pH or calcium making the water scale, a dirty or undersized filter, and fine particles such as dust or pollen. Test with a drop kit, raise chlorine to shock level (40% of CYA) if algae is likely, bring pH to 7.2–7.8, clean the filter, and run the pump continuously until it clears.

## About and policies

- [About Pool Water Calculator](https://www.poolwatercalculator.com/about/): Who publishes Pool Water Calculator, what our free pool calculators cover, and how we keep formulas, sources and cost figures accurate and up to date.
- [Calculator Methodology and Sources](https://www.poolwatercalculator.com/methodology/): Pool Water Calculator converts volume at 7.480519 US gallons per cubic foot, doses chlorine from available-chlorine mass (1 ppm = 1 mg/L), estimates acid and soda ash with a closed carbonate-plus-cyanurate buffer model (pK1 6.3, pK2 10.2, CYA pKa 6.88), and computes the saturation index as pH + TF + CF + AF − 12.1. Cost ranges span the lowest low to the highest high across named published guides.
- [Contact Us](https://www.poolwatercalculator.com/contact/): Contact the Pool Water Calculator editorial team to report a correction, a calculator bug or a broken source, or to suggest a new pool calculator.
- [Privacy Policy](https://www.poolwatercalculator.com/privacy-policy/): How Pool Water Calculator handles data: no accounts, calculator inputs stay in your browser, contact messages, hosting logs, and Google AdSense cookies.
- [Terms of Use and Disclaimer](https://www.poolwatercalculator.com/terms/): Terms of use and safety disclaimer for Pool Water Calculator: estimates only, follow product labels, handle pool chemicals safely, and no professional advice.