BYTETOOLS

Pool Chemical Calculator

Dose chlorine, pH, alkalinity, calcium, stabiliser and salt from your test results and pool volume, and check water balance with the Langelier Saturation Index.

Estimates only. Add one chemical at a time, run the pump for the circulation period, then retest before adding anything else. Never mix pool chemicals together or pour water into acid, and follow the label on the container over anything shown here.

Current and target readings

Dosing list

ParameterChangeProductAdd
Free chlorinePour slowly around the deep end with the pump running.+2.0 ppmLiquid chlorine, 12.5% trade strength30.7 fl oz
pH (lower)Also drops total alkalinity by about 4 ppm.7.80 → 7.50Muriatic acid, 31.45% (20° Baumé)15.0 fl oz
Total alkalinity (lower)Add in a slug over the deep end, then aerate to bring pH back up.-20 ppmMuriatic acid, 31.45% (20° Baumé)76.8 fl oz
Calcium hardness (raise)Dissolves exothermically — add to water, never water to product.+100 ppmCalcium chloride flake, 77%18.05 lb
Stabiliser / CYA (raise)Slow to dissolve — sock it in the skimmer and leave the pump running.+20 ppmCyanuric acid granules2.50 lb

Order of work: alkalinity first, then pH, then calcium, then stabiliser, then chlorine. Alkalinity and pH move together, so re-test after each one rather than dosing everything in a single afternoon.

0.31
Langelier Saturation Index
Scaling — calcium will deposit on surfaces and the heater
Water balance
56,781
Pool volume (litres)

Doses come from the mass of active ingredient the water needs: grams = ppm change × litres ÷ 1,000, adjusted by the product's equivalent weight and its purity. pH doses are solved from the carbonate equilibrium at your alkalinity rather than a flat rule of thumb, which is why the same pH move needs different acid at TA 80 and TA 120. The index uses LSI = pH + temperature factor + (log₁₀ calcium − 0.4) + log₁₀ carbonate alkalinity − a TDS constant, with −0.3 to +0.3 taken as balanced. Real pools outgas CO₂ and rebound, so a pH dose usually needs a second, smaller top-up. Not a substitute for testing.

What is the Pool Chemical Calculator?

The ByteTools Pool Chemical Calculator turns a test kit reading into a dosing list. Enter your pool volume and the current and target figures for free chlorine, pH, total alkalinity, calcium hardness, cyanuric acid and salt, and it works out how much of each product to add — in pounds and ounces or in kilograms, grams and millilitres.

  • Doses for chlorine, pH, alkalinity, calcium, stabiliser and salt from your own readings
  • pH solved from the carbonate equilibrium at your alkalinity, not a fixed rule of thumb
  • Product picker covering cal-hypo, dichlor, trichlor, liquid chlorine, muriatic and dry acid
  • Side effects flagged: alkalinity shifts from soda ash and acid, stabiliser from dichlor and trichlor
  • Langelier Saturation Index with a corrosive, balanced or scaling verdict
  • Copyable dosing list; everything computed in your browser with nothing uploaded

How to use the Pool Chemical Calculator

  1. 1

    Choose gallons or litres, enter your pool volume, and pick whether doses are shown in US or metric units.

  2. 2

    Fill in the current and target readings for chlorine, pH, alkalinity, calcium hardness and cyanuric acid from your test kit.

  3. 3

    Select which chlorine, acid and calcium products you actually have, and tick the salt option if you run a chlorine generator.

  4. 4

    Read the dosing table — it lists the change, the product and the amount, with a note on each chemical's side effects.

  5. 5

    Check the Langelier Saturation Index at the bottom, then copy the dosing list to take out to the pool.

About the Pool Chemical Calculator

The ByteTools Pool Chemical Calculator turns a test kit reading into a dosing list. Enter your pool volume and the current and target figures for free chlorine, pH, total alkalinity, calcium hardness, cyanuric acid and salt, and it works out how much of each product to add — in pounds and ounces or in kilograms, grams and millilitres.

The pH doses are solved from the carbonate equilibrium at your actual alkalinity rather than a flat rule of thumb, which is why the same pH move needs different amounts of acid at 80 ppm and at 120 ppm of alkalinity. Side effects are spelled out too: soda ash raises alkalinity, acid lowers it, and dichlor and trichlor add stabiliser you did not ask for.

It also reports the Langelier Saturation Index so you can see whether the water is corrosive, balanced or scaling. Everything runs locally in your browser. These are estimates only — add one chemical at a time, circulate, retest, and follow the label on the container over anything shown here.

Frequently asked questions

How much chlorine do I add to a 10,000 gallon pool?

To raise free chlorine by 1 ppm you need about 2 ounces of 65% cal-hypo, or about 10 fluid ounces of 12.5% liquid chlorine. The calculator scales that to your pool volume and to the exact gap between your current and target readings.

How much muriatic acid do I need to lower my pool pH?

It depends on alkalinity, not just on the pH gap. Moving 10,000 gallons from pH 8.0 to 7.5 at 100 ppm alkalinity takes roughly 12 to 13 fluid ounces of 31.45% muriatic acid; the same move at 80 ppm needs about 10. That is why alkalinity is an input here.

How much baking soda raises pool alkalinity?

About 1.4 pounds of sodium bicarbonate per 10,000 gallons raises total alkalinity by 10 ppm. That comes straight from the chemistry — bicarbonate has an equivalent weight of 84 against alkalinity measured as calcium carbonate at 50.

What is a good Langelier Saturation Index for a pool?

Anywhere from −0.3 to +0.3 is generally considered balanced. Below that the water is aggressive and will etch plaster and dissolve grout; above it calcium deposits on surfaces, heaters and salt cells. The index combines pH, temperature, calcium, alkalinity and total dissolved solids.

Why does my pH keep rising after I add acid?

Because acid converts bicarbonate to dissolved carbon dioxide, which then outgasses to the air and lets the pH rebound. This calculator assumes no outgassing, so a real pool usually needs a second, smaller top-up. Aeration accelerates the rebound, which is useful when you want alkalinity down but pH steady.

In what order should I add pool chemicals?

Alkalinity first, then pH, then calcium hardness, then stabiliser, then chlorine. Add one at a time, run the pump through a full turnover, and retest before the next. Never mix products together, and always add chemical to water rather than water to chemical.

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