Pool chemical dosing calculator
Your gallons + your test strip numbers → exactly how much chlorine, baking soda, stabilizer, calcium or salt to add. Updated August 2026.
1 · Your pool's volume
Working with 20,000 gallons
2 · What are you fixing?
Ideal Free Chlorine: 1–3 ppm (shock: 10–12 ppm). Adjusting pH? Doses aren't linear — see soda ash / muriatic acid.
3 · Add one of these
Slightly raises pH. Loses strength in storage — buy fresh, store cool and dark.
Adds ~0.7 ppm calcium hardness per 1 ppm FC — avoid if your CH is already high. Slightly raises pH.
Adds ~0.9 ppm CYA per 1 ppm FC — CYA builds up fast. Fine early season, switch to liquid or cal-hypo once CYA hits 30–50.
Adds ~0.6 ppm CYA per 1 ppm FC and is strongly acidic — expect pH and alkalinity to drift down with steady tab use.
Estimates from standard label dosing, to raise Free Chlorine by 2.5 ppm in 20,000 gallons. Add ½–⅔ of the dose first, circulate 4–6 hours, retest, then top up. Never mix chemicals with each other.
Know your chemicals
What each one does, exact dosing tables by pool size, and the safety rules that matter.
The workhorse of pool sanitizing: fast-acting, adds no stabilizer and no calcium. Ideal for regular chlorination and shocking pools that already have enough CYA.
🧨 Cal-Hypo Shock (65–73%)The standard granular shock. Strong, unstabilized chlorine — great for weekly shocking and algae kills where CYA is already sufficient.
🧂 Dichlor Granules (56%)Stabilized granular chlorine — pH-neutral and gentle on surfaces, but every dose also raises your stabilizer. Best for new fills and spas.
⚪ Trichlor Tablets (90%)The slow-release tablet in your floater. Convenient steady chlorination, but it acidifies the water and stacks CYA over a season — plan around both.
🥄 Baking SodaThe alkalinity raiser. 1.4 lb per 10,000 gallons lifts TA by 10 ppm. Low TA makes pH bounce around — fix TA first, then chase pH.
📈 Soda AshThe pH raiser. pH chemistry is non-linear, so treat doses as starting points: ~6 oz per 10,000 gallons raises pH about 0.2 when alkalinity is near 100 ppm.
⚠️ Muriatic Acid (31.45%)The pH (and alkalinity) reducer. Cheap and effective, but the most dangerous bottle on your shelf — the safety rules are not optional.
☀️ Cyanuric Acid (Stabilizer)Sunscreen for your chlorine: without 30–50 ppm CYA, UV burns off outdoor-pool chlorine in hours. But it only goes up — dose carefully.
🪨 Calcium Chloride (77%)Protects plaster and equipment: water below ~200 ppm calcium is aggressive and pulls calcium out of plaster, grout and heat exchangers.
🧊 Pool SaltFor saltwater-generator pools: most cells want ~3,200 ppm. A typical 10,000-gallon fresh fill needs roughly 265 lb of salt to get there.
Questions, answered
How do I calculate my pool's volume?+
Length × width × average depth × 7.5 for rectangles (5.9 for round pools, 6.7 for ovals) gives gallons. Average depth is (shallow end + deep end) ÷ 2. A 30×15 ft pool averaging 5 ft deep holds about 16,900 gallons.
How much chlorine do I add to my pool?+
To raise free chlorine by 1 ppm in 10,000 gallons: about 10.7 fl oz of 12.5% liquid chlorine, 2 oz of cal-hypo shock, or 2.4 oz of dichlor. Most pools target 1–3 ppm for daily sanitizing and 10–12 ppm when shocking.
In what order should I fix my pool chemistry?+
Alkalinity first (80–120 ppm), because low TA makes pH unstable. Then pH (7.4–7.6), then stabilizer (30–50 ppm CYA), then chlorine. Calcium and salt can be adjusted anytime.
Which pool chemicals must never be mixed?+
None of them, ever — but two combinations are actively dangerous: trichlor + cal-hypo can ignite or explode even from residue in a scoop, and any chlorine + acid releases toxic chlorine gas. Add each chemical separately, hours apart, with the pump running.
Why does my chlorine disappear so fast?+
Usually no stabilizer: without 30–50 ppm cyanuric acid, sunlight destroys most free chlorine within hours. If CYA is fine but chlorine still vanishes overnight, you likely have an algae or ammonia demand — shock the pool.