Free tool

Pool Chemical Calculator

One test, every dose, in the right order.

How these numbers are worked out, and the sources behind them: see our methodology. Updated 2026-10-21.

Ideal pool chemistry ranges

Target ranges for residential pool water
Reading	Target	Notes
Free chlorine (FC)	About 7.5% of CYA (3 to 5 ppm at 40 CYA)	Shock at about 40% of CYA
Combined chlorine (CC)	0 to 0.5 ppm	Above 0.5 means it's time to shock
pH	7.4 to 7.6	7.2 to 7.8 is acceptable
Total alkalinity (TA)	80 to 120 ppm	60 to 80 for salt pools
Calcium hardness (CH)	250 to 400 ppm plaster; 175 to 250 vinyl	150 to 250 for spas
Cyanuric acid (CYA)	30 to 50 ppm	60 to 80 for salt; 0 to 30 indoors
Salt	2,700 to 3,400 ppm	Salt pools only; check your cell's range
Water temperature	78 to 84°F	Affects LSI and how fast chlorine burns off

Worked example

A 15,000 gallon plaster pool tests at pH 7.9, alkalinity 70, free chlorine 1 and CYA 40. With 12.5% liquid chlorine and 31.45% muriatic acid, the plan is:

Alkalinity 70 to 100: about 6.75 lb of baking soda. Circulate 6 hours and retest.
pH 7.9 to 7.5: about 96 fl oz (3 quarts) of muriatic acid, split into two doses. Retest in 4 to 6 hours.
Free chlorine 1 to 4.6 (the target for CYA 40): about 55 fl oz of liquid chlorine.
Calcium, stabilizer and salt: already on target, nothing to add.

How each dose is calculated

Liquid chlorine: gallons of product = ppm rise x pool gallons / 1,000,000 / strength
Granular chlorine: lb = ppm rise x pool gallons x 8.34 / 1,000,000 / strength
Baking soda: lb = pool gallons / 10,000 x TA rise / 10 x 1.5
Muriatic acid (31.45%): fl oz = pool gallons / 10,000 x pH drop / 0.2 x 32 x TA / 100
Soda ash: oz = pool gallons / 10,000 x pH rise / 0.2 x 6 x TA / 100
Calcium chloride (77%): lb = pool gallons / 10,000 x CH rise / 10 x 1.25
Stabilizer: oz = 0.0013 x pool gallons x CYA rise
Salt: lb = pool gallons x salt rise x 8.34 / 1,000,000

Strength is a fraction: 12.5% is 0.125. Each row links to its own calculator for the details.

Pool chemicals you'll need

Chlorine: liquid chlorine or bleach for daily dosing; cal-hypo, dichlor or trichlor tabs if you prefer solids (they add calcium or CYA). Chlorine calculator
Muriatic acid or dry acid: lowers pH and alkalinity. pH calculator
Baking soda and soda ash: raise alkalinity and pH. Alkalinity calculator
Calcium chloride: raises calcium hardness. Calcium calculator
Stabilizer (cyanuric acid): protects chlorine from sunlight. Stabilizer calculator
Pool salt: for salt chlorine generators. Salt calculator

How to use this calculator

1
Pick your pool type and units
Chlorine, saltwater, vinyl or spa sets sensible targets. Choose gallons or litres.
2
Enter your pool volume
Don't know it? Use the Pool Volume Calculator first. Every dose scales from this number.
3
Enter each current reading
Free chlorine, pH, alkalinity, calcium, stabilizer and salt from your test kit or strips.
4
Choose your products
Pick your chlorine type and strength, acid, and alkalinity product. The chlorine target follows your CYA.
5
Work through the plan in order
Add one chemical at a time, wait the time shown, and retest before the next step.

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Frequently asked

Pool chemical calculator questions

What order should I add pool chemicals?

Alkalinity first, because it buffers pH. Then pH, then chlorine, then calcium, stabilizer and salt. Add one chemical at a time, run the pump so it circulates, and retest before dosing again.

What are the ideal pool chemistry levels?

Free chlorine about 7.5% of your CYA (3 to 5 ppm at 40 CYA), pH 7.4 to 7.6, alkalinity 80 to 120 ppm, calcium 200 to 400 ppm, CYA 30 to 50 ppm (60 to 80 for salt) and salt 2,700 to 3,400 ppm in a salt pool. The table below has the full list.

How long after adding chemicals can I swim?

Usually 30 minutes after acid, baking soda or liquid chlorine with the pump running, once pH reads 7.2 to 7.8 and free chlorine is under 10 ppm. Wait about an hour after calcium chloride, and after a shock wait until chlorine drops back under 10 ppm.

Can I add chlorine and acid at the same time?

No. Mixing chlorine and acid releases chlorine gas. Add them at different times and in different spots, with the pump running, and let the first one circulate for at least 15 to 30 minutes before the second.

How much chlorine for a 10,000, 15,000 or 20,000 gallon pool?

To raise free chlorine 3 ppm with 12.5% liquid chlorine: about 31 fl oz (1 quart) for 10,000 gallons, 46 fl oz for 15,000 and 61 fl oz (about half a gallon) for 20,000. Use about 25% more of 10% chlorine, or about twice as much 6% bleach.

Can I use this for a hot tub or spa?

Yes. Pick the spa preset and enter the spa's gallons. Spa volumes are small, so a little chemical moves the numbers a lot. Measure carefully and retest after each addition.

How is each dose calculated?

Every row uses the same dosing figures as Skimmer's single-chemical calculators. For example, 1 gallon of 12.5% liquid chlorine raises 10,000 gallons by about 12.5 ppm, and 1.5 lb of baking soda raises alkalinity about 10 ppm per 10,000 gallons. See the formulas below.

Can I lower a reading that's too high?

pH and alkalinity come down with acid (alkalinity uses the slow aerate method). No chemical removes calcium, stabilizer or salt; the only way to lower those is to drain part of the pool and refill with fresh water. The plan flags which is which.