Pool Chlorine Calculator — Measured Adjustment

Estimate a measured free-chlorine adjustment from your pool volume, test reading, chosen target and the exact strength unit on your product label.

Measured water · measured free chlorine · your product label

Plan a chlorine adjustment

See the theoretical amount to raise free chlorine from your test reading to a target you choose. Retest the water before swimming.

Enter your measurements

Pool and test reading

Use current water volume, not the pool's empty shell capacity. Enter free chlorine, not total chlorine.

Current water volumeUS gallons. Measure my pool volume →Measured free chlorineLatest test result, in ppmYour target free chlorineIn ppm; check product label and local rules

Read your product label

Select the wording and units actually printed on your product. A sodium hypochlorite percentage is different from available chlorine.

Label statesIf the label uses other units, do not guess.Available chlorine on labelg/L of product; example only

The example 120 g/L is editable. Use your own label's value; old or heat-exposed liquid may be weaker than its printed strength.

Theoretical product amount315.5 mL · 10.7 US fl oz

For 10,000 US gal, from 1 to 2 ppm using 120 g/L available chlorine.

Available chlorine needed37.85 g10,000 × 3.785411784 L/gal × 1 mg/L ÷ 1,000 = 37.85 g

This is an ideal mixing estimate. Sunlight, organic demand, pH and stabilizer can change the measured result. Follow the product label, circulate as directed, then retest.

Use the result carefully

Test first. Free chlorine and pH are separate readings. CDC advises at least 1 ppm free chlorine in a home pool, or at least 2 ppm when cyanuric acid is used, with pH 7.0–7.8. A local rule or product label may differ.
Match the exact label unit. This calculator needs available chlorine per liter or by weight, or sodium hypochlorite by weight. A liquid percentage cannot become fluid ounces without density.
Follow the label and retest. Never mix chlorine with acid or another pool chemical. The calculated rise is not a promise of the final test reading or a fixed daily dose.

How is the estimate calculated?

For water, a change of 1 ppm is approximately 1 mg of available chlorine per liter. Multiply pool liters by the desired ppm rise, then divide by 1,000 to get grams of available chlorine. Divide by the label's available-chlorine concentration. If a label instead reports sodium hypochlorite mass %, multiply that fraction by 70.906 / 74.442 to express chlorine-equivalent mass. For a liquid weight percentage, product density converts weight to volume only when supplied. The tool does not model chlorine demand, pH effects, cyanuric acid, or the accumulation of calcium/stabilizer from a particular product.

For a current reading at or above your target, the tool shows “No addition indicated” and no product dose. If a DPD test reads unexpectedly low after a very high dose, CDC notes that readings above 10 ppm can bleach the reagent and appear falsely low.

Sources: CDC home pool water treatment · CDC chemical safety · EPA example sodium hypochlorite product label · NIST gallon conversion. Always use the directions on your own product.

Enable JavaScript to edit this example. For 10,000 US gallons, a rise from 1 to 2 ppm requires 37.85 g of available chlorine. At 120 g/L, that is about 315.5 mL (10.7 US fl oz) of liquid product. Retest after following its label.