Muriatic acid calculator
Enter your current and target pH, your total alkalinity, and pool volume to get the exact amount of muriatic acid to add — and how much alkalinity it will also lower.
How much muriatic acid to lower pH?
The amount depends on how far you’re dropping pH and — crucially — your total alkalinity, which buffers the water. Higher alkalinity needs more acid for the same pH change. This calculator models the actual carbonate buffer system, so it’s accurate across the whole range, and it tells you how much alkalinity the dose also removes.
Acid lowers alkalinity too
Muriatic acid lowers both pH and total alkalinity. If your alkalinity is also high, that’s convenient. If alkalinity is already fine, add acid to the deep end and then aerate (fountains, jets, returns pointed up) to bring pH back up while alkalinity stays down.
Safety first
Always add acid to water, never water to acid. Pour slowly into the deep end with the pump running, wear gloves and eye protection, and never mix acid with chlorine — it produces toxic chlorine gas. Re-test before adding more.
Ideal ranges
| Level | Target | Notes |
|---|---|---|
| Ideal pH | 7.4–7.6 | Best comfort + chlorine efficiency |
| Acceptable | 7.2–7.8 | |
| Total alkalinity | 60–120 ppm | Lower end limits pH drift |
Frequently asked questions
What strength muriatic acid does this assume?
You can pick 31.45% (full strength), 14.5% (low-fume), or dry acid in the calculator. The default is 31.45%.
My pH keeps rising — why?
Usually high alkalinity or aeration (common in salt pools and spas). Lowering alkalinity to the low end of the range makes pH much more stable.
Related calculators & guides
Get exact doses, saved and on schedule
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