Pool Shock Calculator
Shocking your pool kills bacteria, breaks down combined chlorine, and clears cloudy or green water. Enter your pool volume and select your water condition — this calculator gives you the exact amount of calcium hypochlorite shock to add.
Your dosage will appear here
Enter your pool volume and readings, then click calculate.
Need to dial in chlorine, pH, or alkalinity too? See the full pool chemical calculator →
Quick Answer
For normal maintenance, use 1 lb of cal-hypo shock per 10,000 gallons. Double the dose for cloudy water, and triple it for green/algae water.
How It Works: Formula & Variables
lbs of cal-hypo shock = (Gallons / 10,000) × Shock Factor
Shock factor: 1 for normal maintenance, 2 for cloudy water, 3 for green/algae water.
Worked Examples
Example: Green pool
A 15,000-gallon pool has turned green. Dose = (15,000 / 10,000) × 3 = 4.5 lbs of cal-hypo shock.
Key Concepts
Shock vs. daily chlorine: Shock is a large one-time dose to break down contaminants and combined chlorine — it's not a substitute for ongoing sanitizer.
Always shock at night: UV rays burn off unstabilised chlorine before it can fully work.
Common Mistakes
Swimming too soon: Wait until free chlorine drops below 5 ppm before swimming again.
Shocking without brushing first: For green pools, brush the walls and floor before shocking so the chemical can reach trapped algae.
Frequently Asked Questions
A severely green pool needs triple-shock treatment — 3 lbs of cal-hypo per 10,000 gallons. Brush the walls first, run the pump continuously, and repeat after 24 hours if the water hasn't cleared.
Yes. Use 1 gallon of liquid chlorine (10-12.5%) per 10,000 gallons for a standard shock. For green pools, triple the dose. Liquid chlorine works faster but dissipates more quickly than granular.
Shock once a week during swim season, after heavy rain, after a pool party, or whenever chlorine demand spikes. Always shock at night.