ConverterHub

Pool Chlorine Dosage Calculator

Enter your pool volume, current and target chlorine, and product strength.

How it is calculated

The tool converts the pool volume from US gallons to litres (× 3.785), works out how much available chlorine must be added, and divides by the strength of your product. Since 1 ppm is 1 mg per litre: chlorine needed (g) = (target ppm − current ppm) × litres ÷ 1000 and product dose (g) = chlorine needed ÷ (strength % ÷ 100). The dose is also shown in ounces (grams ÷ 28.35). The target must be higher than the current level; if it is equal or lower, no result is shown because nothing needs to be added. Volume and strength must be above zero. The dose is a weight of product, not a volume, and the calculation covers only free chlorine, with no allowance for chlorine demand from sunlight, swimmers or organic matter, or for any change in pH or stabilizer.

Worked example

A 15,000-gallon pool tests 1 ppm free chlorine and you want 3 ppm, using a 12.5% product. Litres = 15,000 × 3.785 = 56,775. Chlorine needed = (3 − 1) × 56,775 ÷ 1000 = 113.55 g. Product dose = 113.55 ÷ 0.125 = 908.4 g, which is 32.04 oz. With a 65% product, the same job needs only about 174.7 g.

Try this example →

Common mistakes

  • Entering the volume in litres or cubic metres. The field is in US gallons; a 56,775-litre pool is 15,000 gallons.
  • Entering the strength as a decimal (0.125) instead of a percentage (12.5). The field expects percent.
  • Using the target level as the amount to add. The tool subtracts the current reading itself, so enter your measured chlorine level as current.
  • Treating the grams as a liquid volume. Liquid chlorine is usually measured by volume, so convert the weight using the density on the product label.
  • Adding the full dose at once with no retest. Chlorine is consumed continually, so test again after circulation and adjust.

About this calculator

Raising a pool’s free chlorine to a target level is a mass-balance calculation: the chlorine deficit (target ppm minus current ppm) multiplied by the pool’s volume gives the total mass of available chlorine needed, and dividing that by the chosen product’s percent available chlorine converts it into the actual amount of product to add — whether that’s liquid chlorine (typically 10–12.5% sodium hypochlorite), calcium hypochlorite (around 65–73% available chlorine), or a dichlor/trichlor product with its own labeled strength.

Because different chlorine products have very different concentrations and some also affect pH or add cyanuric acid stabilizer, pool operators and Certified Pool Operators (CPOs) need this conversion to avoid under- or over-chlorinating, which can mean anything from ineffective sanitation to bather irritation and equipment damage.

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