How do I properly calculate how much chlorine to add to my pool?

First, test your pool water with a drop-based test kit to get your current free chlorine level. Then find your pool’s volume in gallons (length × width × average depth × 7.5 for irregular shapes, rounding down). Use an online pool calculator like Trouble Free Pool or Orenda, entering your pool volume, current level, target level, and liquid chlorine concentration (10% or 12.5%). Add the chlorine slowly near a return jet, never mix with other chemicals, and slightly underdose to avoid turning your pool green or bleaching hair.