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PoolDose

How much chlorine to add to a pool

Multiply the ppm you want to add by the pool volume in cubic metres and you have the grams of active chlorine, then divide by the strength on the label. For 50 m³ and a rise of 1 ppm that is 333 ml of 15% liquid chlorine or 74 g of calcium hypochlorite. Dosing does that sum for the product you own.

3 min read · Updated 2026-10-09

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How is the chlorine dose calculated?

One ppm is one milligram per litre, and a cubic metre is a thousand litres, so raising a 50 m³ pool by 1 ppm takes 50 g of active chlorine. A bottle that says 15% holds 0.15 g of active chlorine per gram or per ml, so you divide: 50 ÷ 0.15 is about 333 ml.

The app uses these strengths: 0.15 and 0.10 for liquid sodium hypochlorite, 0.68 for calcium hypochlorite, 0.90 for trichlor and 0.56 for dichlor. If your label says something else, for example 70% calcium hypochlorite instead of the 68% midpoint, the app's result is off by the same ratio, about 3% in that case.

How do I get the dose in PoolDose?

  1. Set the volume once in Volume and tap Use this volume, or type it straight into Pool volume (m³) on the dosing screen.
  2. Open Dosing and keep Product on Chlorine.
  3. Pick your product under Chlorine source.
  4. Enter Measured (ppm), the free chlorine from your strip, and Target (ppm).
  5. Read the amount under Dose.
Raising free chlorine by 1 ppm in a 50 m³ pool (0 to 1 ppm)
Chlorine sourceAmount
Liquid sodium hypochlorite, 15%333 ml
Liquid sodium hypochlorite, 10%500 ml
Calcium hypochlorite, 65-70%74 g
Trichlor, 90%56 g
Dichlor, 56%89 g

Going from 1 to 3 ppm in the same pool with 15% liquid takes 667 ml. In US units a 13,000 gallon pool going from 1 to 3 ppm shows 22.2 fl oz of 15% liquid, or 5.1 oz of calcium hypochlorite.

What target should I type?

Use what your product label, equipment or local rules ask for. For reference, the Assistant starts with a 2 ppm target and the shaded band in the Log charts is 1 to 3 ppm.

Type the free chlorine from your strip as the measured value, not total chlorine.

How do I add it and check the result?

  • Dose in the evening or with the pump running, never with swimmers in the water. The Guide tab says the same.
  • Measure the product with a jug or scale you use only for chemicals, and put it into water, not water onto it. Dissolve solids as the label says.
  • Wait for the pump to circulate the water, test again, and only then decide whether another small top-up is needed.
  • Type the new reading as Measured (ppm). The new Dose is just the gap that is left.

What does the number not know about my pool?

  • It ignores chlorine the sun and swimmers have already used up, so the real rise can be smaller.
  • It does not model what the product leaves behind: trichlor and dichlor add stabilizer, calcium hypochlorite adds hardness. Check those readings now and then, because stabilizer and hardness only go up when you add them.
  • There is no shock mode. If your product label calls for a higher target, type that number yourself in Target (ppm).

Questions and answers

How much liquid chlorine raises a pool by 1 ppm?
For a 50 m³ pool, 333 ml of 15% sodium hypochlorite or 500 ml of 10%. The rule is volume in cubic metres times ppm, divided by the strength as a fraction.
Can I use this for a pool in gallons?
Yes. Switch Settings > Units to US and type the volume in gallons. The result appears in fluid ounces, or gallons from 128 fl oz up.
Does it include shock doses?
There is no shock button. You can type a higher target yourself, but pick it from the product label.
Why does trichlor need so few grams?
Because it is about 90% available chlorine, so less product gives the same active chlorine. The app does not account for the stabilizer it adds.

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