How much chlorine to add to your pool
The right amount depends on three things: how big your pool is, how far your current level is below target, and the strength of the product you're using. Here's the plain version, with examples.
The target: 1–3 ppm free chlorine
Aim for 1–3 ppmfree chlorine, with about 2 ppm as a comfortable middle. Below 1 ppm the water isn't protected and algae gets a foothold; much above 3 ppm it's harsh on eyes and skin. You're always dosing to close the gap between where you are and that target — not to a fixed “capful per swim”.
The rule of thumb
Granular cal-hypo (around 65% available chlorine) takes roughly 1.5 g per 1,000 L (per m³) to raise free chlorine by about 1 ppm. Liquid chlorine and other products differ, so the honest answer is: read the dosing line on yourproduct and scale it to your pool. That's exactly what the calculator below does.
- ~38,000 L (10,000 gal): ~57 g of cal-hypo to raise 1 ppm.
- ~57,000 L (15,000 gal): ~85 g to raise 1 ppm.
- ~76,000 L (20,000 gal): ~114 g to raise 1 ppm.
Multiply by how many ppm you need to climb — going from 0.5 to 2 ppm is a 1.5 ppm jump. Not sure of your volume? Measure it first with the pool volume calculator.
Work out your exact dose
Numbers in hand? This free calculator turns them into the exact amount for your pool's size:
Chlorine Dosage CalculatorHow much chlorine to add to reach the right level.Frequently asked
- How much chlorine for a 10,000 gallon pool?
- To raise free chlorine by 1 ppm, roughly 57 g of 65% cal-hypo. Multiply by how far below 2 ppm you are — e.g. from 0.5 ppm that's about a 1.5 ppm jump, so ~85 g. Always use your own product's dosing figure for accuracy.
- I added chlorine and it still reads zero — why?
- Something is consuming it: algae, organics, or heavy bather load create a 'chlorine demand'. If a normal dose vanishes within hours, you likely need to shock the pool to burn that demand out, then it will start holding.
- Can I add too much chlorine?
- Yes. Above ~3 ppm it stings eyes and skin; very high levels bleach swimwear. You can't easily remove it — stop dosing and let sunlight and time bring it down, then re-test before swimming.
- Does stabiliser (CYA) change the dose?
- It changes how well chlorine holds, not the raw dose to move ppm. Cyanuric acid shields chlorine from the sun so it lasts longer; too much and you'll need a higher free-chlorine target to stay effective.
More pool help
- Common pool problems — Green, cloudy, low chlorine, drifting pH — what's wrong and how to fix it.
- Why your pool turned green — Green water is algae from low chlorine — the step-by-step fix and how long it takes.
- How to lower your pool's pH — Pool pH too high? Why it matters and how to bring it back to 7.2–7.6.
- How to raise your pool's pH — Pool pH too low? Acidic water stings and corrodes — how to bring it back up.
- Cloudy pool water — Clear but not green? The three usual causes and how to get back to clear.
- Chlorine won't hold — Chlorine crashing to zero is a demand to shock out — how to diagnose and fix it.
- How much shock to add — Reach shock level (10–15 ppm) to clear the water — what it means and how much.
Stop guessing, start swimming
Algae Later reads your pH and chlorine, tells you exactly what to add, and nudges you when it's time to test again.
Set up your pool — free