Stop guessing your pool chlorine. Test first, then use a calculator.

You need three numbers: your pool’s volume in gallons, your current free chlorine level, and your target level. Then use an online pool calculator.

Guessing is how you end up with a green swamp or bleached hair. A decent test kit (drop-based, not strips) is non-negotiable. Most people don’t know their exact pool volume either—if you have an irregular shape, measure length × width × average depth × 7.5 (for gallons). Round down. It’s better to slightly underdose and test again.

Liquid chlorine concentrations vary—10% or 12.5% are common. The calculator accounts for that. I use the one from Trouble Free Pool or Orenda. Bookmark it. Add the chlorine slowly near a return jet, not all at once in one spot. Never mix with other chemicals, especially acid.

You will not memorize the formula, and you shouldn’t try. Digital calculators are free and more accurate than your best guess.

Your pool will thank you, and so will your wallet.