Pool Chemical Calculator

Pool owners spend too long guessing how much chlorine, shock, or pH adjuster to add after testing their water. Enter your pool volume and current readings — this calculator gives you exact doses for every chemical in one step. Works for above-ground and inground pools, in gallons or liters.

Pool Details

Pool volume

Units

Pool type

Current free chlorine (ppm)

Target free chlorine (ppm)

Chlorine source

Your dosage will appear here

Enter your pool volume and readings, then click calculate.

How the Calculations Work

Every dose is based on how many 10,000-gallon units your pool contains, multiplied by the standard treatment amount for each chemical. The chlorine formula adjusts automatically for your chosen sanitiser — liquid chlorine, granular, or household bleach each have different active concentrations. pH and alkalinity doses follow guidelines from the Pool & Hot Tub Alliance (PHTA).

Dosage reference: amounts needed to treat one 10,000-gallon increment

Chemical	10,000 gal	15,000 gal	20,000 gal	25,000 gal	30,000 gal
Liquid chlorine (+1 ppm)	12.8 oz	19.2 oz	25.6 oz	32.0 oz	38.4 oz
Granular chlorine (+1 ppm)	2.0 oz	3.0 oz	4.0 oz	5.0 oz	6.0 oz
Shock (normal dose)	1.0 lbs	1.5 lbs	2.0 lbs	2.5 lbs	3.0 lbs
pH Up (+0.4 pH)	12.0 oz	18.0 oz	24.0 oz	30.0 oz	36.0 oz
Baking soda (+20 ppm alkalinity)	3.0 lbs	4.5 lbs	6.0 lbs	7.5 lbs	9.0 lbs

Safety note Always add chemicals directly to pool water — never mix chemicals together before adding. Add chemicals to the deep end with the pump running. Never add two different chemicals at the same time. Store chemicals in a cool, dry place away from children.

Quick Answer

Enter your pool volume and current chlorine, pH, or alkalinity reading, choose your chemical source, and the calculator gives you the exact amount to add — in ounces or pounds — to bring your water into the ideal range.

How It Works: Formula & Variables

Dose = (Target − Current) × (Gallons / 10,000) × Chemical Factor

Liquid chlorine (10–12.5%): oz = (target − current) × (gallons / 10,000) × 12.8
Granular dichlor (56%): oz = (target − current) × (gallons / 10,000) × 2
Cal-hypo shock (68%): lbs = (gallons / 10,000) × shock factor (1, 2, or 3)
Soda ash (pH Up): oz = ((7.4 − pH) / 0.2) × (gallons / 10,000) × 6
Muriatic acid (pH Down): fl oz = ((pH − 7.4) / 0.2) × (gallons / 10,000) × 10
Baking soda (alkalinity): lbs = ((100 − alkalinity) / 10) × (gallons / 10,000) × 1.5

Worked Examples

Example 1: Raising chlorine

A 10,000-gallon pool reads 1 ppm free chlorine and needs to reach 3 ppm using liquid chlorine (10–12.5%). Dose = (3 − 1) × (10,000 / 10,000) × 12.8 = 25.6 oz.

Example 2: Lowering pH

A 15,000-gallon pool reads pH 7.8. Dose = ((7.8 − 7.4) / 0.2) × (15,000 / 10,000) × 10 ≈ 30 fl oz of muriatic acid.

Key Concepts

Free chlorine: The active sanitiser available to kill bacteria and algae. Ideal range is 1–3 ppm outdoor, 3–5 ppm indoor.

Total alkalinity as a buffer: Alkalinity stabilises pH — if it's out of range (80–120 ppm), pH will swing unpredictably even after correction.

Shock vs. daily sanitiser: Shock is a large one-time dose used to break down contaminants, not a substitute for regular chlorine maintenance.

Common Mistakes

Adjusting pH before alkalinity: If alkalinity is below 80 ppm, raise it first — pH adjustments won't hold otherwise.

Mixing chemicals together: Always add one chemical at a time and let the pump circulate for 30 minutes before adding another.

Shocking during the day: Sunlight burns off unstabilised chlorine before it can work — always shock at night.

Frequently Asked Questions

Test your water 2–3 times per week during swim season. Add chemicals only when readings fall outside target ranges — over-treating is as harmful as under-treating.

No. Add one chemical, run the pump for 30 minutes, then retest before adding another. Mixing chemicals in the water can cause dangerous reactions and inaccurate results.

Always shock at night or dusk. UV rays from sunlight destroy unstabilised chlorine rapidly, wasting the shock before it can work.

Wait until free chlorine drops back below 5 ppm — typically 8–24 hours depending on pool size and shock dose. Retest before swimming.

Cloudy water after shock usually means dead algae or debris in suspension. Run your filter continuously and backwash if pressure rises. Clarity typically returns within 24–48 hours.

Overdosing acid drops pH and alkalinity sharply, which can etch plaster, corrode metal fittings, and irritate skin. If overdosed, add baking soda gradually and retest every 30 minutes.

Last reviewed 2026-06-21. For educational purposes only — not professional advice.