Pool Chlorine Calculator

Find out exactly how much chlorine to add to your pool. Enter your pool volume, current and target chlorine levels, and select your chlorine product.

How to Calculate Chlorine for Your Pool

Maintaining the right chlorine level keeps your pool water safe and clear. The ideal free chlorine range for most residential pools is 1–3 ppm, with 3 ppm being the recommended target.

Understanding Chlorine Products

  • Liquid Chlorine (Sodium Hypochlorite 10%) — the most common form for daily dosing. Measured in fluid ounces or gallons. Acts fast but degrades quickly in sunlight.
  • Dichlor (56% Available Chlorine) — granular, stabilized chlorine that dissolves quickly. Contains cyanuric acid, so it adds stabilizer as it sanitizes.
  • Trichlor Tablets (90% Available Chlorine) — slow-dissolving tablets used in floating dispensers or inline chlorinators. Also contains cyanuric acid.
  • Calcium Hypochlorite / Cal-Hypo (65% Available Chlorine) — granular, unstabilized chlorine. Strong and affordable, but raises calcium hardness over time.

The Dosing Formula

All chlorine dosing starts from the same base calculation:

Weight of pure chlorine (lbs) = (Pool Gallons × PPM Increase) ÷ 7,525

The constant 7,525 represents the number of gallons of water that 1 pound of pure chlorine will raise by 1 ppm. From there, divide by the product's available chlorine percentage to get the actual product weight needed, then convert to the appropriate unit (ounces, pounds, or fluid ounces).

Tips for Adding Chlorine

  • Always add chlorine in the evening or at night to reduce UV degradation.
  • Run your pump for at least 30 minutes after adding chlorine to distribute it evenly.
  • Never mix different chlorine products together — this can cause dangerous chemical reactions.
  • Test your water 24 hours after treatment to confirm the chlorine level has reached your target.