How the pool ph calculator works
pH is a scale, not an amount, so the dose depends on how much your water resists change. That resistance is total alkalinity, which is why the calculator asks for it.
To bring pH down you add muriatic acid or dry acid. To bring it up you add soda ash. The tool picks the right one based on which direction you are moving.
The formula, step by step
Dose = pH Change x (Alkalinity / 100) x (Gallons / 10,000) x Product Rate
- Find the change: target pH minus current pH.
- Scale by alkalinity, since 100 ppm is the baseline.
- Scale by pool size in units of 10,000 gallons.
- Lowering uses 26 fluid ounces of muriatic acid per 0.4 pH drop at that baseline.
- Raising uses 6 ounces of soda ash per 0.2 pH rise at that baseline.
Worked example
A 20,000 gallon pool reads pH 8.0 with 120 ppm alkalinity, and you want pH 7.5.
Change = 0.5. Alkalinity factor = 1.2. Size factor = 2.0.
Muriatic acid = 0.5 x 26 / 0.4 x 1.2 x 2.0, which lands near 78 fluid ounces, so a bit over half a gallon.
Watch it done
This short video walks through the same job in real life, so you can match what you see on screen to what you do at the pool.
Tips before you start
Add acid in two halves. Pour the first half, run the pump for four hours, retest, then decide if the rest is needed. Overshooting into the low 6s is hard on plaster and eyes.
High pH usually follows a fresh plaster job, an aerating water feature or a saltwater generator. Fix the alkalinity first and pH tends to settle on its own.
Pool pH Calculator FAQs
What pH should a pool be?
Aim for 7.4 to 7.6. That range is comfortable for swimmers and keeps chlorine working at a good strength.
How do I lower pH in a pool?
Add muriatic acid or dry acid in front of a return with the pump running. Retest four hours later, before you add any more.
Why does my pH keep rising?
Aeration drives it up. Waterfalls, spa jets and salt cells all push carbon dioxide out of the water, which raises pH every week.