Pool Chlorine Calculator
Calculate how much liquid chlorine to add to raise your pool's chlorine level, for both routine maintenance dosing and shock treatment.
How this calculator works
Chlorine dosing comes down to how much pool water you have and how far you want to raise the chlorine level, measured in parts per million (ppm). This calculator converts that ppm rise into pounds of pure (100%-available) chlorine, then adjusts for the actual strength of the product you’re using, since most liquid chlorine isn’t 100% strength.
Formula: Pounds of 100%-available chlorine needed = pool gallons × target ppm rise × 0.00000834. For a product that’s less than 100% strength (like 10% liquid chlorine), divide that figure by the product’s strength (as a decimal).
Worked example
Maintenance dose — a 20,000-gallon pool, raising chlorine by 3 ppm, using 10% liquid chlorine:
- Pure chlorine needed: 20,000 × 3 × 0.00000834 = 0.5004 lb
- Adjusted for 10% strength: 0.5004 ÷ 0.10 = 5.00 lb (80.06 oz) of 10% liquid chlorine
Shock dose — the same 20,000-gallon pool, raising chlorine by 10 ppm, using 10% liquid chlorine:
- 16.68 lb (266.88 oz) of product
Notes
A routine maintenance dose targets a small ppm rise, often 1-3 ppm, just to keep chlorine in its normal working range from day to day. Shock treatment targets a much bigger jump, commonly around 10 ppm, to burn off chloramines and other contaminants after heavy swimmer load, algae, or a rain storm that dilutes and dirties the water.
Always add chlorine at dusk or after dark. Sunlight burns off unstabilized chlorine fast, so dosing during the day wastes product and leaves the pool under-treated by the time you actually need the chlorine to be working.
How to use
Enter your pool’s gallons, your current chlorine reading, and your target chlorine level, then select or enter your product’s strength. Use a small target rise for routine maintenance and a larger one, around 10 ppm, when shocking the pool after heavy use or contamination.
Pool chemistry estimates only. Always test your water and follow your specific product’s label — actual dose depends on the product’s exact strength and your test results.
Frequently asked questions
How much liquid chlorine do I add to my pool?
It depends on your pool's gallons, how many ppm you want to raise, and your product's strength. This calculator multiplies pool gallons by the target ppm rise and a fixed weight factor to get pounds of 100% chlorine, then divides by your product's strength (like 10%) to get the actual dose of that product.
What's the difference between a maintenance dose and a shock dose?
A maintenance dose raises chlorine by a small amount, often 1-3 ppm, to keep it in range day to day. A shock dose targets a much bigger jump, commonly around 10 ppm, to burn off chloramines and contaminants after heavy pool use, algae, or a storm.
Why does chlorine strength matter for dosing?
A product's strength tells you how much of the bottle is actually available chlorine versus water and other ingredients. A 10% liquid chlorine needs ten times the volume of a 100%-available product to deliver the same ppm rise, so plugging in the wrong strength will throw off your dose significantly.
When is the best time to add chlorine to a pool?
Add chlorine at dusk or after dark. Sunlight breaks down unstabilized chlorine quickly, so a dose added in full sun loses potency before it has a chance to work. Adding it in the evening lets it circulate and work overnight.
Estimates only. Verify quantities with your supplier before purchasing.