Pool Alkalinity Calculator
Find out how much baking soda raises your pool's total alkalinity to the level you want, or how much muriatic acid or dry acid lowers it. Enter the pool volume and your test results for an exact dose in US and metric units.
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Not sure? Use the pool volume calculator.
From a TA test kit or strip (ppm = mg/L as CaCO3).
Many pool guides aim for 80-120 ppm.
How to use the Pool Alkalinity Calculator
- Enter the pool volume in US gallons or liters.
- Test total alkalinity and enter the current reading and your target (often 80-120 ppm).
- Pick the product you have: baking soda to raise TA, or muriatic or dry acid to lower it.
- Read the dose and, for big changes, add it in the suggested parts.
- Circulate and retest after about 6 hours before adding more.
Pool alkalinity formula
Total alkalinity (TA) is reported in ppm as calcium carbonate (CaCO3). One equivalent of alkalinity is 50.04 g of CaCO3, so:
equivalents = ppm change × pool liters ÷ 50,043
Each equivalent is supplied by 84.0 g of baking soda (NaHCO3) or 53.0 g of soda ash (Na2CO3), and removed by 36.46 g of hydrochloric acid (about 100 mL of 31.45% muriatic acid) or about 129 g of 93% sodium bisulfate.
Example: raise a 15,000 gallon pool (56,781 L) from 70 to 100 ppm. Equivalents = 30 × 56,781 ÷ 50,043 = 34.0 eq. Baking soda = 34.0 × 84.0 = 2,860 g = 6.3 lb.
Dose per 10 ppm of total alkalinity
| Product | 5,000 gal | 10,000 gal | 15,000 gal | 20,000 gal |
|---|---|---|---|---|
| Baking soda (raise) | 0.70 lb | 1.40 lb | 2.10 lb | 2.80 lb |
| Soda ash (raise, also raises pH) | 0.44 lb | 0.88 lb | 1.33 lb | 1.77 lb |
| Muriatic acid 31.45% (lower) | 12.8 fl oz | 25.6 fl oz | 38.4 fl oz | 51.3 fl oz |
| Muriatic acid 14.5% (lower) | 30.0 fl oz | 60.1 fl oz | 90.1 fl oz | 120 fl oz |
| Dry acid, sodium bisulfate (lower) | 1.07 lb | 2.15 lb | 3.22 lb | 4.30 lb |
Figures use pure products. Older or bargain products may be weaker, which is one more reason to add in parts and retest.
Tips for adjusting alkalinity
- Fix alkalinity before pH. TA buffers pH, so adjusting pH first is often undone when you change TA afterwards.
- Dissolve or broadcast baking soda across the deep end with the pump running. It may cloud the water briefly; that clears as it dissolves.
- Add big doses in parts. For changes over about 30 ppm, split the dose, wait about 6 hours of circulation and retest before each part.
- Handle acid with care. Wear gloves and eye protection, add acid to water (never the reverse), pour slowly near a return jet, and store it away from chlorine.
- Retest regularly. Rain, top-up water and acid used to lower pH all shift TA over a season, so check it at least every week or two.
Frequently asked questions
How much baking soda raises alkalinity by 10 ppm?
About 1.4 lb (635 g) of baking soda raises total alkalinity by 10 ppm in 10,000 US gallons. Many pool charts round this to 1.5 lb. For a 20,000 gallon pool, double it to about 2.8 lb.
How much muriatic acid lowers alkalinity?
About 25.6 fl oz (760 mL) of 31.45% muriatic acid lowers total alkalinity by 10 ppm in 10,000 US gallons. Half-strength 14.5% acid needs about 60 fl oz, and dry acid (sodium bisulfate) about 2.15 lb for the same change.
What should total alkalinity be in a pool?
Many pool guides recommend 80-120 ppm. Lower values let pH swing and can etch plaster, while higher values make pH drift upward and can contribute to scale and cloudy water. Some saltwater and stabilized pools run slightly lower; follow the guidance for your surface and sanitizer.
Is baking soda the same as alkalinity increaser?
Yes. Alkalinity increaser sold for pools is sodium bicarbonate, the same chemical as household baking soda. Plain baking soda works the same way and is often cheaper per pound.
Should I use baking soda or soda ash?
Baking soda raises alkalinity with only a small rise in pH. Soda ash (sodium carbonate) raises alkalinity too, but raises pH a lot more, so it suits water where both pH and alkalinity are low.
Why does lowering alkalinity also lower pH?
Acid neutralizes alkalinity and lowers pH at the same time. To bring TA down without leaving the pH too low, add acid to reach a pH of about 7.0-7.2, then aerate the water to let carbon dioxide escape, which raises pH without raising TA, and repeat.
How is the dose calculated?
Alkalinity is measured as mg/L of calcium carbonate, and 50.04 mg of CaCO3 is one milliequivalent. The calculator finds the milliequivalents to add or remove (ppm change × liters ÷ 50.04) and converts them to product: 84 g of baking soda, 53 g of soda ash, or 36.5 g of HCl per equivalent.
Are all the tools on FreeToolCabin tested for quality and accuracy?
Yes! Every tool on our site undergoes automated Q/A testing in real browser environments to ensure high precision, correct output, and zero errors. If you happen to spot a bug or have a suggestion, please contact us at [email protected] and our team will review it right away.