Muriatic Acid Pool Calculator
High pH causes chlorine to become ineffective and can leave scale on pool surfaces. Enter your pool volume and current pH — this calculator tells you exactly how much muriatic acid (hydrochloric acid) to add to bring your water back into range.
Your dosage will appear here
Enter your pool volume and readings, then click calculate.
Need to dial in chlorine, shock, or alkalinity too? See the full pool chemical calculator →
Quick Answer
Enter your pool volume and current pH — the calculator gives you the exact fluid ounces of muriatic acid (31.45%) needed to bring pH back to 7.4.
How It Works: Formula & Variables
fl oz = ((Current pH − 7.4) / 0.2) × (Gallons / 10,000) × 10
Based on muriatic acid at 31.45% concentration.
Worked Examples
Example: High pH
A 15,000-gallon pool reads pH 7.8. Dose = ((7.8 − 7.4) / 0.2) × (15,000 / 10,000) × 10 ≈ 30 fl oz of muriatic acid.
Key Concepts
Alkalinity as a buffer: If total alkalinity is above 120 ppm, it will keep pushing pH back up — lower alkalinity first for a lasting fix.
Always dilute and add slowly: Add acid near a return jet with the pump running to disperse it evenly and avoid localized corrosion.
Common Mistakes
Pouring water into acid: Always pour acid into water, never the reverse — this can cause a violent reaction.
Overdosing in one go: Add in smaller increments and retest after 30 minutes rather than dumping the full calculated dose at once for large corrections.
Frequently Asked Questions
Wait at least 30 minutes with the pump running, then retest pH. If pH is in the 7.2–7.6 range, it is safe to swim. If you added a large dose, wait 1–2 hours.
Yes. Sodium bisulfate (dry acid) is safer to handle and produces the same result. Use approximately 3/4 lb of dry acid per 10,000 gallons to lower pH by 0.2 as an alternative to 10 fl oz of muriatic acid.
High total alkalinity acts as a pH buffer, pushing pH up over time. If your alkalinity is above 120 ppm, lower that first — it will stabilise pH naturally.