What is the ideal free chlorine level for a pool?

Residential pools should maintain 2–4 ppm (parts per million) of free chlorine. Levels below 1 ppm are unsafe; levels above 10 ppm can irritate skin and eyes.

What is the difference between granular and liquid chlorine?

Granular chlorine (calcium hypochlorite, ~65% available chlorine) is solid and dissolves in water. Liquid chlorine (sodium hypochlorite, ~10% available chlorine) is pre-dissolved bleach. Both sanitize effectively; granular raises calcium hardness slightly while liquid does not.

Why does pool size affect the dose so much?

ppm (parts per million) means milligrams per liter. A larger pool volume requires proportionally more product to raise the concentration by the same amount. Twice the volume needs twice the chlorine.

When is the best time to add chlorine?

Add chlorine in the evening or at dusk. UV sunlight degrades free chlorine rapidly, so daytime additions lose effectiveness quickly. Running the pump for several hours after adding ensures even distribution.

Can I mix granular chlorine directly into the pool?

Pre-dissolve granular chlorine in a bucket of water first, then pour the solution around the pool perimeter. Never add chlorine directly to the skimmer or mix it with other chemicals.

Pool Chlorine Calculator

Calculate exactly how much granular or liquid chlorine to add to your pool based on volume, current level, and target level.

Pool Details

Pool Volume

Current Free Chlorine (ppm)

Target Free Chlorine (ppm)

Recommended: 2–4 ppm for residential pools

Chlorine Type

Granular

65% Ca(ClO)₂

Liquid Bleach

10% NaOCl

Dosage Result

Fill in the details and click Calculate to see results.

Quick Reference

Level (ppm)	Status	Action
0 – 0.9	Unsafe	Shock immediately
1 – 1.9	Low	Add chlorine
2 – 4	Ideal	Maintain
4 – 10	High	Let it drop naturally
> 10	Too High	Do not swim; dilute

Summary

Calculate exactly how much granular or liquid chlorine to add to your pool based on volume, current level, and target level.

How it works

Enter your pool volume in gallons or liters.
Input your current free chlorine reading (from a test kit or strips).
Set your target chlorine level (typically 2–4 ppm for residential pools).
Select chlorine type: granular (65% calcium hypochlorite) or liquid bleach (10%).
Click Calculate to see how much product to add.
The result updates instantly; re-test after 30 minutes of circulation.

Use cases

Shock a pool after heavy rain or a pool party.
Bring chlorine levels up after a low test-kit reading.
Calculate chemical dosage for a newly filled pool.
Determine liquid bleach equivalent to a granular chlorine dose.
Plan chemical purchases before the swimming season.
Maintain safe sanitizer levels for above-ground or in-ground pools.

Frequently Asked Questions

Last updated: 2026-09-19 · Reviewed by Nham Vu