Pool Chlorine Calculator
Enter your pool volume, current and target free chlorine (FC), and the product you're using — we'll tell you exactly how much to add.
Amount to add
Safety first
- Never mix chemicals together.
- Always add the chemical to the water — never water to the chemical.
- Wear gloves and eye protection when handling pool/spa chemicals.
- Keep chemicals out of reach of children and pets.
- Always follow the product label — it overrides any guidance here.
How it's calculated
Start with the grams of available chlorine needed to move your pool from its current FC to your target, based on volume. For liquid chlorine, that converts to a volume (mL/fl oz) using the product's trade %. For granular products (cal-hypo, dichlor, trichlor), it converts to a weight (g/oz) using the product's purity, and we flag the side effect on calcium hardness or CYA.
Ideal free chlorine range
Free chlorine should generally stay around 7.5% of your CYA level (5% for salt pools), with a hard floor of 1 ppm. Use the Stabilizer (CYA) Calculator to find your target.
Frequently asked questions
Which chlorine product should I use?
Liquid chlorine (bleach) doesn't add anything else to your water besides a small, temporary pH bump. Cal-hypo adds calcium hardness. Dichlor and trichlor add cyanuric acid (CYA) — great for a new pool, but they will push your CYA too high if used as your everyday chlorine source.
What does "trade %" mean on liquid chlorine?
It's the percentage of available chlorine per 100 mL, printed on the jug. Supermarket bleach is usually labeled in weight %, which is slightly different — we convert it for you, but double-check your label if the numbers look off.
How much chlorine should I add?
Enter your current and target FC (free chlorine) reading, and we calculate the dose for your pool volume and chosen product.
Will this raise my CYA or calcium too much?
We show you the side effect for the product you pick. If you use dichlor or trichlor regularly, your CYA will climb over time — switch to liquid chlorine once your CYA is in range.