How do you calculate pool shock dose?

Multiply pool volume in 10,000-gallon units by the ppm rise, by the product's units per ppm per 10k gal, by an efficiency correction. For a 20,000-gallon pool (2.0) raising 10 ppm at 0.143 with 1.18 correction, that is about 3.37 lb.

How much shock do I need for a 20,000 gallon pool?

To raise free chlorine 10 ppm with 68% cal-hypo (0.143 lb per ppm per 10k gal) and an 1.18 efficiency correction, a 20,000-gallon pool needs about 3.37 lb. Algae treatments target higher ppm and need more.

What ppm should I shock a pool to?

Routine oxidation targets about a 10 ppm free-chlorine rise. Algae kills need 20-30 ppm or higher, and chloramine breakpoint requires roughly 10 times the combined chlorine reading, pick your ppm target to match the goal.

Cal-hypo vs liquid chlorine for shocking, which is better?

Cal-hypo is high-strength and economical but adds calcium and needs dissolving. Liquid chlorine (sodium hypochlorite) adds no calcium and mixes instantly but is weaker per volume. Enter the correct yield factor for whichever you use.

Why doesn't my pool clear after shocking?

Common causes are under-dosing below breakpoint, high stabilizer (cyanuric acid) blunting the chlorine, or heavy demand from algae and debris. Verify the ppm target matched the job and retest before re-dosing.

What does the efficiency correction do in the shock formula?

It offsets oxidizer lost to demand, sunlight, and undissolved product so the water actually reaches the target ppm. Enter 100 divided by expected efficiency; at 85% you enter 1.18, which raises the example base dose from 2.86 lb to about 3.37 lb.

Pool, Spa & Water Treatment Chemistry calculator

Pool Shock Treatment Dose Calculator

Shocking (super-chlorination) raises free chlorine high enough to oxidize organic waste, kill algae, and break apart combined chloramines that cause the harsh 'chlorine smell.' This calculator converts your pool volume, the ppm rise you're targeting, and the product's yield factor into the pounds or gallons of shock to add, with an efficiency correction for real-world losses. Service techs and pool owners use it because a shock that's too weak fails to reach breakpoint and just wastes product, while an overdose can bleach liners and spike pH. Sizing the dose to the job, routine 10 ppm oxidation versus a 30 ppm algae kill, is the difference between clear water tomorrow and a repeat treatment.

What this calculator does

Estimate shock treatment dose from water volume, desired oxidizer rise, product strength, and efficiency.
Use it after heavy use, algae cleanup, combined chlorine, or contamination response planning.
It calculates the pounds or gallons of shock to add by multiplying pool volume (in 10k-gal units), the target ppm rise, the product yield factor, and an efficiency correction.

Formula used

Shock dose = pool volume basis x desired oxidizer increase x product dose factor x efficiency correction

Inputs explained

Pool volume basis (gallons / 10,000): Divide pool gallons by 10,000. For a 20,000-gallon pool, enter 2.
Target free chlorine rise: Use the target ppm increase. Most shock events target 10 to 30 ppm free chlorine.
Product oxidizer yield factor: Use label dose factor. Typical 68% calcium hypochlorite yields about 0.143 lb per ppm per 10,000 gallons.
Delivery efficiency correction: Enter 100 divided by expected delivery efficiency. For 85% efficiency, enter 1.18.

How to use the result

Use it for weekly oxidation, after heavy bather load or rain, to break chloramines at breakpoint, or to hit the high free-chlorine levels needed for an algae kill.
It sizes the oxidizer dose but does not compute breakpoint chlorination, which requires roughly 10x the combined chlorine reading, for chloramine removal, verify you're clearing breakpoint, not just adding a fixed ppm.

Current U.S. benchmarks

Global copper trades at $13,552 per tonne (IMF via FRED, Jun 2026), up 37.8% in a year, and U.S. industrial electricity averages 8.66 cents per kWh. Both feed electrified-hardware unit economics.

Common questions

How do you calculate pool shock dose? Multiply pool volume in 10,000-gallon units by the ppm rise, by the product's units per ppm per 10k gal, by an efficiency correction. For a 20,000-gallon pool (2.0) raising 10 ppm at 0.143 with 1.18 correction, that is about 3.37 lb.
How much shock do I need for a 20,000 gallon pool? To raise free chlorine 10 ppm with 68% cal-hypo (0.143 lb per ppm per 10k gal) and an 1.18 efficiency correction, a 20,000-gallon pool needs about 3.37 lb. Algae treatments target higher ppm and need more.
What ppm should I shock a pool to? Routine oxidation targets about a 10 ppm free-chlorine rise. Algae kills need 20-30 ppm or higher, and chloramine breakpoint requires roughly 10 times the combined chlorine reading, pick your ppm target to match the goal.
Cal-hypo vs liquid chlorine for shocking, which is better? Cal-hypo is high-strength and economical but adds calcium and needs dissolving. Liquid chlorine (sodium hypochlorite) adds no calcium and mixes instantly but is weaker per volume. Enter the correct yield factor for whichever you use.
Why doesn't my pool clear after shocking? Common causes are under-dosing below breakpoint, high stabilizer (cyanuric acid) blunting the chlorine, or heavy demand from algae and debris. Verify the ppm target matched the job and retest before re-dosing.

Last reviewed 2026-05-12.