Pool chlorine cost calculator: liquid vs. tablets vs. granular
Chlorine products are priced in different units: gallons, pounds, buckets. Their strength varies from 6% to 90%, so the shelf price says little about what a month of chlorine really costs. Enter your pool size, how much chlorine it uses a day, and the prices at your store. The calculator puts every product on the same footing and shows what each one leaves behind in the water.
Your prices
Enter the price and size of the package you'd buy. Leave a row blank to skip its cost.
| Product | Price ($) | Package size |
|---|---|---|
| Liquid chlorine 12.5% | gal | |
| Liquid chlorine 10% | gal | |
| Bleach 6% (unscented) | gal | |
| Cal-hypo 65% | lb | |
| Dichlor 56% | lb | |
| Trichlor tablets 90% | lb |
Every product for this period
| Product | Amount | Cost | Also adds |
|---|
Don't know your volume? Use the pool volume calculator.
How much chlorine does a pool use per day?
It varies a lot. Sunlight, water temperature, swimmers, debris and your stabilizer level all change it. Pools with little stabilizer in strong sun can lose most of their chlorine in a few hours. The best way to find your number is to measure it: test free chlorine at the same time on two consecutive days without adding any in between, and take the difference. Do it on a typical day, not right after a storm or a pool party. The default of 3 ppm a day is only a starting point.
How the calculation works
Product amount = chlorine needed ÷ available chlorine (%)
Cost = product amount ÷ package size × package price
Each product is converted by its available chlorine: 12.5% and 10% for liquid chlorine and 6% for bleach (grams per 100 mL), and 65% for cal-hypo, 56% for dichlor and 90% for trichlor (by weight). Labels vary a little, so check yours. The "also adds" column comes from each product's chemistry. Per 1 ppm of chlorine, trichlor leaves about 0.6 ppm of stabilizer (CYA), dichlor about 0.9 ppm, and cal-hypo about 0.7 ppm of calcium hardness. Liquid chlorine and bleach leave about 1.65 ppm of salt.
Worked example
A 15,000-gallon pool using 3 ppm a day needs 90 ppm over 30 days. That's 90 × 56,781 L ÷ 1,000 ≈ 5.1 kg of available chlorine. As each product:
| Product | Amount for 30 days | Also adds over 30 days |
|---|---|---|
| Liquid chlorine 12.5% | about 10.8 gal | about 149 ppm salt |
| Bleach 6% | about 22.5 gal | about 149 ppm salt |
| Cal-hypo 65% | about 17.3 lb | about 64 ppm calcium hardness |
| Dichlor 56% | about 20.1 lb | about 81 ppm CYA |
| Trichlor 90% | about 12.5 lb | about 54 ppm CYA |
That last column is the hidden cost. A pool that starts the season at 30 ppm CYA and runs only on trichlor would pass 80 ppm within a month at this usage. As CYA rises, the pool needs a higher chlorine level to stay clear, and eventually a partial drain to bring CYA back down. Our drain and refill calculator shows how much water that takes.
Choosing between them
- Liquid chlorine or bleach: can be the cheapest per ppm, especially where pool stores sell liquid chlorine in bulk, so compare with your prices above. Nothing builds up except salt. The downsides are weight, storage space, and losing strength over time, faster in heat. Buy it fresh, and keep it cool and out of the sun.
- Trichlor tablets: the most convenient, in a floater or feeder. They're acidic, lowering pH and alkalinity, and they add stabilizer with every dose. Many owners use them early in the season, while CYA is low, then switch to liquid.
- Cal-hypo: useful for shocking and in pools with soft water. In hard-water areas, the added calcium can push the water toward scale.
- Dichlor: dissolves quickly and is close to pH-neutral. Handy for raising CYA and chlorine together at startup, but it builds CYA fastest of all.
- Salt chlorine generator: makes chlorine from salt, so there's no chlorine to buy, but you pay for the equipment, electricity and replacement cells every few years. Compare those costs with the yearly chlorine cost this calculator gives you.
Frequently asked questions
Is household bleach cheaper than pool liquid chlorine?
Not always. Bleach is weaker, so you need about twice as much 6% bleach as 12.5% liquid chlorine. Compare the price per gallon divided by its strength, or let the calculator do it. Use only plain, unscented bleach.
Why does my liquid chlorine seem weaker than the label?
Sodium hypochlorite slowly breaks down in the container, faster in heat and sunlight. Older or warm-stored jugs can be noticeably weaker than labeled. If doses raise chlorine less than the calculators predict, that's a likely reason.
Can I mix tablets and liquid chlorine?
Yes, in the pool, as long as they're added separately. Never mix chlorine products with each other outside the pool. Dry products in particular can react violently together. See our chemical safety guide.