Pool Shock Calculator

How much pool shock you need, and why

Shocking a pool means adding a large dose of chlorine (or a non-chlorine oxidizer) all at once to burn off contaminants like combined chlorine (chloramines), algae and organic waste that regular daily chlorine can't fully keep up with. The standard rule is about 1 lb of cal-hypo shock per 10,000 gallons for routine maintenance shocking, done weekly or after heavy pool use.

An algae bloom or a heavily neglected pool typically needs a much bigger dose -- 2 to 3 lb per 10,000 gallons -- to overwhelm the algae and clear cloudy or green water. Severe, established algae sometimes needs repeated heavy shocks over several days along with brushing and filtration.

Cal-hypo (calcium hypochlorite) is the most common shock chemical and is used as the reference dose here; other shock products (like dichlor-based or non-chlorine potassium monopersulfate shock) use different concentrations, so check your product's label for its own recommended rate if you're using something other than plain cal-hypo.

Where these numbers come from

The formulas and default values in this calculator are based on:

• standard pool shock dosing rates published by pool-supply retailers and chemical manufacturers (1 lb cal-hypo per 10,000 gal for routine maintenance shock
• 2-3 lb per 10,000 gal for algae or heavy shock treatment)

These are planning estimates. Test your actual water, follow product labels, and check your equipment manufacturer's guidance before you buy or dose chemicals.