Pool Chemical Calculator

Enter your pool size and test readings to see how much of each chemical to add, and which readings are in range.

You typeWe calculate

How it's calculated

Dose = chart amount per 10,000 gal
     × (gallons ÷ 10,000)
     × (change ÷ chart step)
Chlorine: 1.3 fl oz ÷ strength (liquid)
          1.33 oz ÷ strength (dry)

Chart amounts come from the Pool & Hot Tub Alliance and state and county health department dose tables. The pH line is an approximation.

Sources and worked example

Chlorine to add39 fl ozof Liquid chlorine 10%, free chlorine 1 → 3 ppm

Chlorine: adjust

Readings in range1 of 5

Chlorine for 1 ppm20 fl oz

Pool volume15,000 gal

Chlorine side effectRaises pH, adds salt

What to add, in order
Reading and product	Amount	Status
Total alkalinity 70 → 90 ppmBaking soda (sodium bicarbonate)Raises pH slightly too.	4.2 lb	Adjust
pH 7.8 → 7.5Muriatic acid 31.45%Approximate: high alkalinity needs more acid. Add in stages and retest after the water circulates.	30 fl oz	Adjust
Free chlorine 1 → 3 ppmLiquid chlorine 10%Pour slowly in front of a return.	39 fl oz	Adjust
Stabilizer (CYA) 40 → 40 ppm	None needed	In range
Calcium hardness 180 → 250 ppmCalcium chloride 77%Dissolve in a bucket of water first; it gets hot.	12.6 lb	Adjust

Safety: add one chemical at a time with swimmers out, never mix chemicals, add chemical to water (never water to chemical), and follow the label.

An estimate from published dose charts, not professional advice. Follow the product label, never mix chemicals, and always add chemical to water, never water to chemical.

The full template

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How the pool chemical calculator works

Pool chemical makers and health departments publish dose charts for 10,000 gallons. Each line says how much of a product moves one reading by a set step, such as 1 ppm of chlorine or 10 ppm of alkalinity. This calculator scales those chart amounts to your pool and to the change you need.

1. Find your gallons

Use the size helper if you don't know your volume. A rectangle holds length × width × average depth × 7.5 gallons, since one cubic foot holds about 7.5 gallons. Round and oval pools use 3.14 × radius × radius, which works out to diameter² × depth × 5.9. Average depth is the shallow end plus the deep end, divided by 2.

2. Test, then pick targets

Enter each reading from your test kit and a target inside the recommended range. The chips compare your current readings with the Pool & Hot Tub Alliance ranges for pools. "In range" means ideal, "Adjust" means acceptable but off ideal, and "Out of range" means outside the minimum or maximum. The CDC asks for at least 1 ppm free chlorine, or at least 2 ppm if you use stabilizer, with pH 7.0 to 7.8. PHTA sets the pH minimum a little higher, at 7.2.

3. Scale the chart dose

The dose is the chart amount × (gallons ÷ 10,000) × (change ÷ chart step). For chlorine, the Indiana Department of Health method divides 1.3 fl oz by the product's strength for liquids, or 1.33 oz by its strength for dry products. That gives 13 fl oz of 10% liquid chlorine per ppm per 10,000 gallons.

4. Add in order and retest

The table lists doses in the order to add them: alkalinity first, since it buffers pH, then pH, chlorine, stabilizer and calcium. Each line is worked out on its own. Acid that lowers alkalinity also lowers pH, so retest pH before adding more acid.

Worked example

A 16 × 25 ft pool with a 5 ft average depth holds 15,000 gal. The test reads free chlorine 1 ppm, pH 7.8, alkalinity 70, calcium 180 and stabilizer 40. The owner uses 10% liquid chlorine, 31.45% muriatic acid and 77% calcium chloride.

Worked example doses for 15,000 gallons
Alkalinity 70 → 90 ppm: 1.4 lb × 1.5 × 2	4.2 lb baking soda
pH 7.8 → 7.5: 13.4 fl oz × 1.5 × 1.5	30 fl oz acid
Free chlorine 1 → 3 ppm: 13 fl oz × 1.5 × 2	39 fl oz chlorine
Stabilizer 40 → 40 ppm	None needed
Calcium 180 → 250 ppm: 1.2 lb × 1.5 × 7	12.6 lb calcium chloride

Only stabilizer is in its ideal range (30 to 50 ppm), so 1 of 5 readings show "In range."

Caveats and where sources differ

The pH dose is approximate. How much acid it takes depends on alkalinity. The Yakima County chart gives 12 fl oz of 35% acid (about 13.4 fl oz of 31.45%) or 1 lb of dry acid to drop pH 0.2 in 10,000 gallons, and notes amounts vary. Add half, circulate, retest, then add more.
Charts round differently. PHTA and Indiana list 1.4 lb of baking soda per 10 ppm of alkalinity; Yakima County lists 1.5 lb. For calcium chloride, PHTA lists 0.9 lb (100%) and 1.2 lb (77%); Yakima lists 1.0 and 1.25 lb. This tool uses the PHTA numbers.
Chlorine products add other things. Dichlor adds about 0.9 ppm of stabilizer and cal-hypo about 0.8 ppm of calcium for each ppm of chlorine (PHTA).
Go in stages. Indiana says to add no more than one quart of acid per 10,000 gallons at a time, and not to raise alkalinity more than about 50 ppm at once.

Safety

Read the label and follow it. Never mix chemicals or use the same scoop for two products. Add acid to water, never water to acid. Dissolve dry products in a bucket of pool water first if the label says to. Add chemicals with swimmers out, and never through the skimmer. Store chlorine and acid apart in a cool, dry place.

Weekly pool maintenance checklist

Test free chlorine and pH several times a week, and after storms or heavy use.
Test alkalinity weekly; test calcium and stabilizer about once a month.
Skim the surface and empty the skimmer and pump baskets.
Brush walls, steps and corners, then vacuum the floor.
Check the filter pressure gauge and clean or backwash when it climbs above its clean reading.
Keep the water level around the middle of the skimmer opening.
Log each test and dose so you can spot trends.

Sources

FAQ

Common questions

How much liquid chlorine raises a pool 1 ppm?

About 13 fl oz of 10% liquid chlorine, or about 10.4 fl oz of 12.5%, per 10,000 gallons. Multiply by your gallons divided by 10,000 and by the ppm you need. Check the product label, since strengths vary.

What should my pool chemical levels be?

The Pool & Hot Tub Alliance lists these ideal ranges for pools: free chlorine 2 to 4 ppm, pH 7.4 to 7.6, total alkalinity 80 to 100 ppm with liquid chlorine or cal-hypo (100 to 120 with dichlor or trichlor), calcium hardness 200 to 400 ppm, and cyanuric acid 30 to 50 ppm. Local codes can differ.

What order should I add pool chemicals in?

Adjust total alkalinity first, because it buffers pH, then pH, then chlorine, stabilizer and calcium. Add one chemical at a time, let the pump circulate it, and retest before the next one.

Can I add chlorine and acid at the same time?

No. Never mix pool chemicals, in the pool or out of it. Chlorine and acid together can release toxic chlorine gas. Add them separately, at different spots, with time to circulate in between.

How do I lower cyanuric acid or calcium hardness?

There is no chemical that removes them. The only way is to drain part of the water and refill with fresh water. The calculator shows roughly how many gallons to replace, assuming your fill water has none.

How do I work out how many gallons my pool holds?

Multiply length by width by average depth (in feet) by 7.5 for a rectangle. For a round pool use diameter times diameter times average depth times 5.9. For an oval use length times width times average depth times 5.9.

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