Pool Shock Calculator
Estimate how many pounds of Calcium Hypochlorite (cal-hypo) shock are required to sanitize your pool water or treat severe green algae blooms.
Pool Parameters
Skip measurements and enter gallons directly
Triples the required chemical chlorine shock dosage
Water Volume
0 Gal
Total pool water capacity
Salt Required
0 Lbs
0 bags (40 lb bags)
Shock Chlorine
0 Lbs
Calcium Hypochlorite dose
Pool Geometry Outline
The Mechanics of Pool Superchlorination & Algae Treatment
"Shocking" a swimming pool refers to the process of raising free chlorine levels significantly beyond standard maintenance limits (superchlorination). This is necessary to break apart chloramines (combined chlorine that smells strongly and causes eye burn), sanitize organic matter, and kill green water algae spores.
The standard chlorine shock chemical is Calcium Hypochlorite (typically 65% active chlorine, or cal-hypo). Standard maintenance shock requires **1 pound of cal-hypo per 10,000 gallons** of pool water, which raises free chlorine levels by approximately 5 to 7 PPM.
Algae Treatment Dosage Adjustments
If your pool water has turned green, cloudy, or has visible algae deposits on the walls, standard superchlorination is insufficient:
- Light Green/Cloudy Water: Double shock required (2 lbs of cal-hypo per 10,000 gallons).
- Dark Green/Algae Blooms: Triple shock required (3 lbs of cal-hypo per 10,000 gallons).
- Black/Infested Water: Quadruple shock required (4 lbs of cal-hypo per 10,000 gallons).
Our calculator features a "Heavy Algae / Green Water" toggle that automatically triples the shock requirement to ensure your sanitization treatment breaks down the algae completely.
Best Practices for Shocking your Pool
Shock your pool at **dusk or night**. Because sunlight contains UV rays that rapidly burn off unstabilized chlorine, shocking during the day wastes chemicals. Dissolve granular shock in a bucket of water before pouring it around the deep end perimeter, and run your pool pump for 12 hours continuously to distribute the chlorine.
Shock FAQs
When should I shock my pool?
You should shock your pool weekly as part of regular maintenance, or after heavy pool use, heavy rain, or when water temperatures rise. You must also shock your pool if you detect combined chlorine levels above 0.5 PPM, or when green algae begins growing on pool surfaces.
How long should I wait to swim after shocking my pool?
You must wait at least 12 to 24 hours after shocking your pool before swimming. Test your pool water using a kit and ensure the free chlorine level has dropped back down to the safe swimming range of 1 to 4 PPM before entering the water.
What is the difference between granular shock and liquid chlorine?
Granular shock (calcium hypochlorite) is dry, highly concentrated, and raises chlorine levels quickly, but it also adds small amounts of calcium to the water. Liquid chlorine (sodium hypochlorite) is poured directly and does not add calcium or stabilizer, but it has a shorter shelf life.