Step 1 — Pool Volume Calculator
Calculate your pool's gallons first — this feeds all other calculators below.
START HERE
Avg depth tip: Add shallow-end depth + deep-end depth and divide by 2. Typical pools: 3.5 ft shallow, 8 ft deep → avg 5.75 ft.
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gallons
Enter your pool dimensions above to calculate volume
pH Adjustment Calculator
Exact muriatic acid or dry acid dose to bring pH to the ideal 7.4.
Chemical
Select your pH and pool volume to see the dose
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Safety first: Always add acid to water — never water to acid. Pre-dilute in a bucket, then pour along pool edges with the pump running. Never add acid and chlorine at the same time. Full pH lowering guide →
Chlorine & Shock Calculator
Raise free chlorine for maintenance or shock a green/algae pool.
Treatment Type
Chemical
Select pool volume and chemical to see the dose
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Shock at night: UV destroys unprotected chlorine fast. Always shock after sundown for best results. Run the filter for 24–48 hours continuously when treating a green pool. Full shock guide →
Total Alkalinity Calculator
Raise alkalinity with baking soda, or lower it with muriatic acid.
Enter alkalinity and pool volume above
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Lowering alkalinity tip: Add muriatic acid in one spot with the pump OFF to let it settle. Then aerate (run jets, waterfall, or a fountain) to bring pH back up without raising alkalinity. Water balance FAQ →
Raising alkalinity: Broadcast baking soda across the deep end with the pump running. Wait 6 hours, then retest before adding more. Ideal range: 80–120 ppm. Water balance FAQ →
CYA / Stabilizer Calculator
Cyanuric acid protects chlorine from UV — target 30–50 ppm for outdoor pools.
⚠️ CYA over 80 ppm detected — partial drain & refill recommended
Enter CYA and pool volume above
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How to add CYA: Place cyanuric acid in a mesh sock in the skimmer basket (not directly in the pool — it's slow-dissolving). Leave the pump running and allow 24 hours to fully dissolve. Retest before adding more. Full stabilizer guide →
Calcium Hardness Calculator
Prevent scale buildup and equipment corrosion — target 200–400 ppm.
⚠️ High calcium — only fix is partial drain & refill with fresh water
Enter calcium and pool volume above
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Calcium chloride tip: Add in small increments — no more than 10 lbs per 10,000 gallons at a time. It heats water as it dissolves; always broadcast with pump running. Retest after 24 hours. Too-high calcium causes cloudy water and scale on equipment.
❓ Frequently Asked Questions
How do I calculate how much muriatic acid to add to my pool?
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The standard dose of muriatic acid (31.45%) to lower pH is approximately 3 oz per 10,000 gallons to drop from 7.6 → 7.4, 7 oz from 7.8 → 7.4, 11 oz from 8.0 → 7.4, 16 oz from 8.2 → 7.4, and 22 oz from 8.4+ → 7.4. Always add acid to water — pre-dilute in a bucket, then pour slowly around the pool edges with the pump running. Never add acid and chlorine at the same time.
📖 Full guide: How to Lower Pool pH →
📖 Full guide: How to Lower Pool pH →
How much pool shock do I need for a green pool?
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For a green pool (algae outbreak), you need triple shock: approximately 3 lbs of Cal-Hypo (65%) per 10,000 gallons. Run the filter continuously for 24–48 hours and brush all surfaces. For maintenance shocking (weekly or after heavy use), 1 lb per 10,000 gallons raises free chlorine about 7 ppm.
📖 Full Pool Shock Guide →
📖 Full Pool Shock Guide →
How much baking soda do I add to raise pool alkalinity?
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Baking soda (sodium bicarbonate) raises total alkalinity at a rate of approximately 1.5 lbs per 10,000 gallons per 10 ppm increase. Example: A 20,000-gallon pool at 60 ppm needs to reach 100 ppm (a 40 ppm rise) → (40 ÷ 10) × 1.5 × (20,000 ÷ 10,000) = 12 lbs of baking soda. Broadcast across the deep end and wait 6 hours before retesting.
📖 Pool Water Balance FAQ →
📖 Pool Water Balance FAQ →
What is the ideal CYA level for an outdoor pool?
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The ideal CYA (cyanuric acid / stabilizer) level for an outdoor chlorinated pool is 30–50 ppm. Levels above 80 ppm significantly reduce chlorine effectiveness — a condition sometimes called "chlorine lock." Above 100 ppm, even high chlorine readings may not sanitize your pool properly. If your CYA is too high, the only reliable fix is a partial drain and refill with fresh water.
📖 Full Pool Stabilizer Guide →
📖 Full Pool Stabilizer Guide →
How do I raise calcium hardness in my pool?
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Add calcium chloride to raise calcium hardness. The dose is approximately 12 oz per 10,000 gallons to raise CH by 10 ppm. The target range is 200–400 ppm. Low calcium (below 150 ppm) causes corrosive water that etches plaster and attacks equipment. If calcium is too high (above 500 ppm), the only solution is dilution — partial drain and refill with fresh water.
📖 Pool Water Balance FAQ →
📖 Pool Water Balance FAQ →
Is this pool chemical calculator really free?
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Yes — PoolDiag's chemical calculators are completely free, instant, and require no account or sign-up. Enter your pool size and current readings and you'll get exact doses immediately. For a full AI-powered water balance analysis covering all parameters at once — including diagnosis, prioritization, and step-by-step instructions — visit the main PoolDiag tool.