How Much Shock Does Your Pool Actually Need? The Dose Tables
Updated September 2026
Quick answer: Shock dose = target chlorine rise × pool volume × product strength — and the target depends on the job: ~10 ppm for routine oxidation, chlorine to 40% of your CYA for green algae, ~60% for mustard. For a 10,000-gallon pool at CYA 40, a green-algae kill (16 ppm target) takes roughly 1.4 gallons of 12.5% liquid chlorine or about 2 lb of cal-hypo — most 'shock didn't work' stories are really 'the dose was a third of that.' Full tables below; our calculator scales everything to your exact gallons.
Pick the target before the product
The three jobs and their free-chlorine targets: routine oxidation after heavy use or storms — raise FC to ~10-12 ppm. Green algae kill — FC to 40% of CYA (at CYA 30 that's 12 ppm, at 50 it's 20). Mustard algae — 60% of CYA. Chloramine cleanup (combined chlorine over 0.5) — roughly 10× the CC reading as an FC rise, which usually lands near routine-shock territory.
That CYA multiplier is the piece the bag instructions skip: stabilizer shields algae along with chlorine, so the more CYA you run, the more chlorine any kill requires. It's also the quiet argument for keeping CYA at 30–50 — every extra 10 ppm of stabilizer makes every future rescue proportionally more expensive.
The translation into product
Liquid chlorine 12.5%: one gallon raises 10,000 gallons by ~12.5 ppm — so a 10-ppm routine shock is ~0.8 gal, a 16-ppm algae kill ~1.3 gal, scaled linearly by your volume. Cal-hypo 65-73%: one pound raises 10,000 gallons ~7-8 ppm — routine ≈ 1.3 lb, algae kill ≈ 2+ lb. Dichlor 56%: one pound ≈ 6.6 ppm per 10,000 gal, and adds ~6 ppm CYA with it — early-season only.
Under-dosing is the epidemic: one retail 1-lb 'shock' bag delivers ~7 ppm to 10,000 gallons — half an algae kill at best, a third of it in a 15,000-gallon pool. Buy for the math, not the bag count: an algae rescue on a typical pool is a multiple-jug or multiple-bag purchase, and it's still cheaper than a month of half-doses that never finish the job.
Delivery details that change the result
Dose at dusk (UV eats unstabilized shock in daylight), pump running and left running, liquid poured slowly around the perimeter, granular pre-dissolved for vinyl and fiberglass. For kills, hold the target: retest a few hours later and top back up — hitting 16 ppm for an hour is not the same as holding it overnight.
The finish line is the overnight hold test from our chlorine-lock guide: when the pool loses less than 1 ppm between dusk and dawn, the demand is dead and normal maintenance resumes. And after any big shock: expect a cloudy day or two while the filter clears the casualties — that's success in progress, not a new problem.
FAQ
How much shock do I need for a green pool?+
Raise free chlorine to 40% of your CYA level and hold it — for a 10,000-gallon pool at CYA 40 that's ~16 ppm: about 1.3 gallons of 12.5% liquid chlorine or 2+ lb of cal-hypo, repeated until chlorine holds overnight.
Is one bag of shock enough?+
Usually not: a 1-lb bag raises 10,000 gallons by only ~7 ppm — adequate for routine oxidation, half-strength for an algae kill, and weaker still in bigger pools. Dose by the math, not the bag.
How long after shocking until the pool clears?+
Chlorine does its killing within hours; clarity takes 1–3 days of continuous filtration while dead material is caught. Keep the pump on 24/7 and clean the filter as pressure rises.