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Pool pH Calculator

Reviewed 2026-04

Calculate how much muriatic acid or soda ash to add. Uses measured alkalinity and CYA for a staged estimate. Confirm your pH test is valid before dosing.

Built on CDC and ANSI pool-water standards

CYA changes active chlorine equilibrium; unstabilized HOCl percentages do not describe a stabilized pool.

Safety:Safety: Wear gloves and eye protection, and always add acid into water, never the other way around (pouring water into concentrated acid causes a violent exothermic splash).
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Industry-standard ideal range: 7.2–7.6. Optimal: 7.4

Alkalinity is what resists a pH change, so it sets how much acid you need — the same pool at 70 ppm and 180 ppm needs very different doses. Acid lowers pH and TA together, so we'll predict that side-effect too.

Stabiliser resists pH change too, so it raises the amount of acid needed. Enter 0 only if measured or known absent. A blank value is unknown.

Does your pool have a salt chlorine generator?

Which acid will you use?

Dry acid is unavailable until you confirm there is no salt cell. Pentair's IntelliChlor manual tells you never to use sodium bisulfate — its by-products build up and damage the cell — and Hayward warns against it too. If you are not sure whether you have one, use muriatic acid.

Read this off the bottle. Full-strength muriatic is 31.45% (20 Baumé); some low-fume products are 14.5% and need roughly twice the volume. We do not link an acid product — buy locally and use the label figure.

Confirm your inputs

Examples remain unconfirmed until you check each value. Confirm fresh test results and your measured pool volume before using a dose. Editing a value clears its confirmation.

Frequently asked questions

What pH range should I use?

Use pH 7.2–7.8 for routine swimming conditions, subject to product instructions and a valid test. This calculator offers correction targets of 7.2–7.6. pH alone does not establish sanitation. Percent HOCl charts for unstabilized water do not describe the active fraction of measured FC when CYA is present.

When is my pH test valid after shocking?

Enter recent FC and the test method, and follow the test instructions. High chlorine can distort phenol-red readings. This tool withholds color/strip-based dosing at FC 10 ppm or above; use a fresh reading within the test’s limits or a calibrated meter rated for the sample. Do not improvise neutralization.

How is acid or soda ash calculated?

The estimate uses measured total alkalinity and CYA in a closed carbonate/cyanurate equilibrium model, with no borates, gas exchange or precipitation. Soda ash adds both carbonate and alkalinity. The first estimate covers at most a 0.2 pH change. Actual water can respond differently: circulate, wait at least four hours or longer if the label requires, retest and calculate again.

How does soda ash affect alkalinity?

Per unit mass, sodium carbonate raises alkalinity more than sodium bicarbonate. There is no universal ounces-per-pH-unit rate. If pH is low but TA is already high, aeration can raise pH by releasing carbon dioxide without adding alkalinity; retest rather than assuming a fixed change.

How should I handle pH chemicals?

Follow the exact product label for protective equipment, application and any dilution. Never mix chemicals or add water to concentrated acid. Use only a formulation labeled for pool use. Dry acid is unsuitable where the salt-cell manual prohibits it. The tool does not link an acid product; verify the strength of a locally purchased product.

Alkalinity Calculator →Chlorine Calculator →

How we calculate this
Our formulas follow ANSI pool-water standards and are validated against CDC pool-water health code guidelines. We show you the math so you can verify every result. Questions or corrections? Please contact us.