Dry Acid to Muriatic Acid Calculator
Convert between dry acid (sodium bisulfate) and muriatic acid — enter your amount and product strength to find the equivalent dose.
Quick reference — dry acid vs muriatic acid
Use the table below as a fast lookup for common amounts. All values assume 93.2% dry acid and 31.45% muriatic acid.
| Dry Acid (93.2%) | Muriatic Acid (31.45%) | Muriatic Acid (14.5%) |
|---|---|---|
| ½ lb (8 oz) | 6 fl oz | 14 fl oz |
| 1 lb | 12 fl oz (1½ cups) | 28 fl oz (3½ cups) |
| 1½ lbs | 18 fl oz (2¼ cups) | 42 fl oz (5¼ cups) |
| 2 lbs | 24 fl oz (3 cups) | 56 fl oz (7 cups) |
| 3 lbs | 36 fl oz (4½ cups) | 84 fl oz (2.6 qts) |
| 5 lbs | 60 fl oz (1.9 qts) | 140 fl oz (4.4 qts) |
Dry acid adds sulfates — muriatic acid does not
Sodium bisulfate leaves sulfate ions (SO₄²⁻) in pool water that accumulate over time. High sulfates corrode metal fittings, damage pool heaters, and etch plaster — especially in saltwater pools. Muriatic acid leaves chloride ions, which are harmless at normal pool concentrations. For most pools, muriatic acid is the better long-term choice. Dry acid is ideal for spas or when fume-free storage is required.
Dry acid vs muriatic acid — when to use each
Dry acid (sodium bisulfate, pH Down, pH Minus) — available in granular or powder form, typically 93.2% purity. Advantages: no fumes, no liquid splash risk, easier to store and transport. Disadvantages: adds sulfates that build up in pool water over time. Best for: spas, hot tubs, small pools, situations where liquid acid storage is inconvenient.
Muriatic acid (hydrochloric acid) — a liquid sold in 31.45% (standard) and 14.5% (diluted/safer) concentrations. Advantages: no sulfate accumulation, cost-effective for large pools, faster-acting. Disadvantages: produces corrosive fumes, requires careful handling and ventilation. Best for: most residential and commercial pools for long-term maintenance.
You can switch between them freely
There is no chemical conflict between switching products mid-season. Use the calculator above to find the equivalent dose and apply the same way — near a return jet with the pump running. If you have been relying on dry acid heavily, periodically check your pool's sulfate level.
How to use muriatic acid safely
- Always pre-dilute in a bucket of pool water before adding to the pool
- Pour acid into water — never water into acid
- Wear eye protection and chemical-resistant gloves
- Add near a return jet with the pump running, not near the skimmer
- Never add more than 1 quart at a time — split large doses and retest
- Wait 30 minutes after adding before retesting pH
How to use dry acid safely
- Pre-dissolve in a bucket of pool water before adding — do not broadcast dry granules directly into a small spa or skimmer
- Wear gloves and eye protection — sodium bisulfate is still an acid in contact with moisture
- Add near a return jet with the pump running
- Do not mix with chlorine products or other pool chemicals
- Wait 30 minutes and retest pH before adding more
Frequently asked questions
Is dry acid the same as muriatic acid?
No — they are different chemicals that accomplish the same thing. Dry acid is sodium bisulfate (NaHSO₄), a granular solid. Muriatic acid is hydrochloric acid (HCl), a liquid. Both lower pH and total alkalinity by releasing hydrogen ions, but their chemistry, handling requirements, and long-term effects on pool water differ.
How much dry acid equals 1 quart of muriatic acid?
1 quart (32 fl oz) of 31.45% muriatic acid is equivalent to about 2.7 lbs of 93.2% dry acid. Use the calculator above for any specific amount or strength.
How much muriatic acid equals 1 lb of dry acid?
1 lb of 93.2% dry acid ≈ 12 fl oz (1½ cups) of 31.45% muriatic acid, or about 28 fl oz of 14.5% muriatic acid. The conversion is based on equal hydrogen ion content — the moles of H⁺ that lower pH and alkalinity.
Does dry acid add sulfates to pool water?
Yes. Every dose of sodium bisulfate adds sulfate ions (SO₄²⁻) that do not dissipate — they accumulate over the season. Elevated sulfates are corrosive to pool heaters, metal fittings, and plaster surfaces. Muriatic acid does not add sulfates. If you regularly use dry acid, test your sulfate level periodically; levels above 300–400 ppm are cause for a partial water replacement.
Can I mix dry acid and muriatic acid together?
No. Never mix any two pool chemicals together — including two acids. Always add chemicals separately to pool water with the pump running, and allow time for them to dilute before adding another chemical.
Which is cheaper — dry acid or muriatic acid?
Muriatic acid is typically less expensive per unit of pH-lowering effect. For a 10,000-gallon pool requiring a 0.4 pH drop, expect to pay significantly less per dose with 31.45% muriatic acid than with an equivalent dry acid dose. Dry acid commands a price premium for the convenience and fume-free handling.
Stop guessing, start tracking.
PoolChem Tracker logs your chemical doses and tracks how pH and alkalinity change after each treatment — so you know exactly what to add next time.
