Calculate how much baking soda is needed to raise pool total alkalinity from current to target ppm by water volume, or the alkalinity a set dose will reach.
- All Chemistry Calculators
- Calcium Saturation Index Calculator
- pH To Hydrogen Ion Concentration Calculator
Alkalinity Increase Formula
This model estimates the mass of sodium bicarbonate or anhydrous sodium carbonate needed for a specified increase in total alkalinity, expressed as ppm (mg/L) as CaCO₃ in dilute water. It is a theoretical balance; the actual product label and measured water chemistry control treatment.
Product mass (g) = water volume (L) × increase (ppm as CaCO₃) × equivalent-mass ratio ÷ 1000 ÷ purity fraction.
The ratios used are 84.0066 ÷ 50.04345 for sodium bicarbonate and 105.9888 ÷ 100.0869 for anhydrous sodium carbonate. Bicarbonate contributes one equivalent per mole; carbonate contributes two. Hydrated carbonate and blends with other active ingredients need different product calculations.
Current-to-target mode uses the positive difference between target and current alkalinity. A target at or below the current value returns zero increaser; it does not calculate how to lower alkalinity. Specified-increase mode uses the entered increase directly. Dose-on-hand mode reverses the balance: increase = product mass × purity ÷ ratio ÷ liters × 1000.
One US gallon is 3.785411784 L and one pound is 453.59237 g. Cups use the entered product mass per cup; the blank-field assumption of 189 g/cup is only a rough historical estimate. Product density, packing and cup size vary, so weighing is more reliable.
Pool Alkalinity Targets and Dose Reference
Choose the target for the pool, sanitizer and product instructions using reliable alkalinity and pH tests. Some product labels use an 80–120 ppm range, while others specify different ranges for different treatment systems. A single range is not a universal treatment instruction. Sodium carbonate also raises pH strongly; this calculator does not predict a fixed pH change.
The following reference assumes pure sodium bicarbonate and shows theoretical mass, rounded to two decimals. Product-label doses may differ.
| Water volume | +10 ppm | +20 ppm | +40 ppm |
|---|---|---|---|
| 5,000 US gal | 0.70 lb | 1.40 lb | 2.80 lb |
| 10,000 US gal | 1.40 lb | 2.80 lb | 5.60 lb |
| 15,000 US gal | 2.10 lb | 4.20 lb | 8.41 lb |
| 20,000 US gal | 2.80 lb | 5.60 lb | 11.21 lb |
Example Calculations
For 15,000 US gallons, raising total alkalinity from 60 to 100 ppm requires a theoretical 3,812.681663 g, or 8.405524 lb (about 8.41 lb), of pure sodium bicarbonate. At 50% active purity with inert remainder, the product mass doubles.
For 10,000 US gallons and a 20 ppm increase, the theoretical mass is 2.801841 lb (about 2.80 lb). For 1,000 L and a 10 ppm increase, it is 16.786732 g of pure sodium bicarbonate or 10.589678 g of pure anhydrous sodium carbonate.
FAQs
How does the portion calculation work?
The count is the desired increase divided by the entered maximum increase per portion, rounded up. A 100 ppm correction with a 10 ppm limit gives ten equal arithmetic portions. The count is not capped at eight. These portions are planning arithmetic, not a direction to add every portion without retesting.
When should I retest?
Follow the actual product label for addition, circulation, retesting and re-entry timing. Retest before further additions. There is no universal six-hour waiting time or fixed pH increase in this calculation.
Is alkalinity increaser the same as baking soda?
Many products use sodium bicarbonate. Check the active ingredient and purity. Sodium carbonate (soda ash) has a different equivalent mass and stronger effect on pH; hydrated washing soda and multi-ingredient products cannot be substituted by name alone.
Can I add too much?
Yes. Calculated endpoint alkalinity assumes complete dissolution and no competing reactions or losses. Use the product label and new water tests to avoid overshooting; this calculator does not determine an acid dose or a safe swimming condition.
Basis: USGS alkalinity equivalents and carbonate and bicarbonate contributions. Follow your own product instructions.
