Chemistry

Chlorine Calculator

Calculate exactly how much liquid chlorine, bleach, or dichlor to add to your pool. Enter your pool volume, current FC level, and target — get instant results.

Chlorine Calculator
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Safety

Always add chemicals to water, never water to chemicals. Never mix chlorine with acid — this produces toxic chlorine gas. Wear gloves and eye protection. Test before and after treatment.

Quick answer

To raise free chlorine, add about 10 fl oz of 12.5% liquid chlorine per 10,000 gallons for every 1 ppm you need. Most pools run best at 1–3 ppm FC, and higher when CYA is elevated. At a normal dose the water is safe to swim in about 15 minutes. Enter your pool's numbers above for the exact amount.

How to Use This Calculator

This calculator uses standard pool chemistry formulas to determine the exact amount of chlorine product needed to raise your pool's Free Chlorine (FC) level. The calculation accounts for your pool volume, current FC reading, target FC level, and the concentration of your chosen chlorine product.

What is Free Chlorine (FC)?

Free Chlorine is the amount of chlorine available to sanitize your pool water. It's different from Total Chlorine, which includes Combined Chlorine (chloramines — the stuff that actually smells and irritates eyes). The ideal FC range for most residential pools is 1-3 ppm, though pools with higher CYA levels may need more.

Ideal Chlorine Levels by Pool Type

Pool Type FC Range Notes
Standard chlorine pool 1–3 ppm With CYA 30-50 ppm
Saltwater pool (SWG) 1–3 ppm SWG maintains FC automatically
High-CYA pool (>50 ppm) 2–5 ppm Higher CYA reduces FC effectiveness
Indoor pool 1–3 ppm No UV loss, lower demand

Frequently Asked Questions

Can I use regular household bleach instead of pool chlorine?
Yes. Regular unscented household bleach (8.25% sodium hypochlorite) is chemically the same as liquid pool chlorine — just a lower concentration. You'll need about 50% more bleach by volume compared to 12.5% liquid chlorine. Avoid bleach with fragrances, thickeners, or "splashless" formulas.
How often should I add chlorine to my pool?
Test your FC levels at least 2-3 times per week (daily in peak summer). Add chlorine whenever FC drops below your minimum target. Most pools lose 1-3 ppm per day from sunlight, swimmer load, and organic matter. Consistent testing and dosing prevents algae and keeps your water safe.
What's the difference between shocking and regular chlorination?
Regular chlorination maintains FC within the normal range (1-3 ppm). Shocking raises FC to 10x your CYA level (breakpoint chlorination) to destroy chloramines and kill algae. Use our Pool Shock Calculator for shock dosing.