About Pool Calculator Hub

What is Pool Calculator Hub

Pool Calculator Hub is a free collection of pool chemistry and equipment calculators. Our calculators tell you exactly what to buy. Not raw numbers, real bags and bottles. Enter your pool dimensions and current chemical readings. We output the specific number of bags, ounces, or hours you need, plus product links to purchase exactly that amount.

This site has no named founder, no paid staff, and no sponsors. We earn a small commission on products purchased through our links.

Our Formula Sources

Chemical mass calculations use unit conversions and molecular/equivalent weights. pH estimates use a bounded carbonate/cyanurate equilibrium model. Routine sanitation guidance references CDC home-pool advice; generator limits come from the named model manuals. Algae targets use the referenced Powell/Falk CYA chart. These are distinct kinds of evidence, and the calculators do not claim that a public-pool standard validates every dose or residential target.

Read the methodology for formulas, worked examples and model limits. Real water can differ from the assumptions; verify the label, use staged additions where specified and recalculate from fresh tests.

Per-Calculator Documentation

Each calculator formula, its sources, and any important correction notes are listed below.

Salt

lb = Δppm × gallons × 8.34 lb/gal ÷ 1,000,000

Sodium chloride mass. Select salt target and limits from the exact cell manual.

Example: 10,000 gal, salt 2,800 → 3,200 ppm (full estimated correction): 33.36 lb.

Dry chlorine / shock

oz by weight = ΔFC ppm × gallons × 8.34 × 16 ÷ (1,000,000 × available-chlorine fraction)

For 65% available chlorine, use fraction 0.65, not ingredient purity 0.68. Divide ounces by 16 for pounds.

Example: 10,000 gal, FC increase 1 ppm, 65% available chlorine: 2.053 oz by weight.

Liquid chlorine

fl oz = ΔFC ppm × gallons × 8.34 × 128 ÷ (1,000,000 × trade percent × 0.08345)

Trade percent is grams available chlorine per 100 mL. Here 10 means 10%, not 0.10. Household bleach labels give sodium hypochlorite weight percent; converting requires density and the Cl₂/NaOCl molar-mass ratio. Ingredient weight percent is not trade percent.

Example: 10,000 gal, FC increase 1 ppm, 10% trade available chlorine: 12.79 fl oz.

pH down

acid equivalents = (initial alkalinity − modeled alkalinity at the next pH) × water volume in litres

Closed carbonate/cyanurate equilibrium at 25°C, with measured TA corrected for cyanurate and water contributions to infer dissolved carbon. HCl equivalents convert using its weight percent and density; sodium bisulfate uses molar mass and purity. One step is at most 0.2 pH; aeration, temperature and unmeasured buffers can change field response.

Example: 10,000 gal, pH 8.0 → first step 7.8, measured TA 100, CYA 0, 31.45% w/w HCl: 3.709 fl oz.

pH up

Solve carbonate/cyanurate equilibrium including 1 mole dissolved carbon and 2 equivalents alkalinity per mole of Na₂CO₃ added

Soda ash is not a fixed ounces-per-pH-change rate. Use measured TA and CYA; one step is at most 0.2 pH. Aeration can raise pH without increasing TA when TA is already high. The model assumes pure sodium carbonate.

Example: 10,000 gal, pH 7.0 → first step 7.2, measured TA 100, CYA 0: 18.32 oz by weight.

Alkalinity

lb NaHCO₃ = ΔTA ppm as CaCO₃ × gallons × 8.34 ÷ 1,000,000 × (84.007 ÷ 50.045)

One mole of bicarbonate supplies one equivalent; a CaCO₃ equivalent is half its molar mass. Assumes pure sodium bicarbonate.

Example: 1,000 gal, TA increase 10 ppm as CaCO₃: 0.14 lb.

CYA

lb = ΔCYA ppm × gallons × 8.34 ÷ (1,000,000 × purity fraction); oz by weight = lb × 16

Granular cyanuric acid purity 98% means fraction 0.98. The calculator starts with 60%, then waits seven days and recalculates from a fresh reading.

Example: 1,000 gal, CYA increase 5 ppm, 98% purity (full estimated correction): 0.04255 lb.

Calcium hardness

lb CaCl₂ product = ΔCH ppm as CaCO₃ × gallons × 8.34 ÷ 1,000,000 × (110.98 ÷ 100.09) ÷ CaCl₂ fraction

Use the product’s actual CaCl₂ content (e.g. 0.77 or 0.94). The chosen hardness target does not by itself establish saturation balance or metal-corrosion risk.

Example: 10,000 gal, CH increase 10 ppm, 77% CaCl₂: 1.201 lb.

Volume and equipment

Geometry uses 7.48 US gal/ft³. Kidney volume is an estimate; L-shaped arms must not overlap. Turnover flow is gallons ÷ (hours × 60); runtime is turnovers × gallons ÷ (GPM × 60). Schedules over 24 hours are infeasible. Annual electricity is watts ÷ 1,000 × hours/day × 365 × price/kWh. Savings require a measured alternative flow and power scenario. Pump selection needs an actual system curve and a named model/RPM curve.

Affiliate Revenue

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