Free calculator: how much baking soda or acid to fix pool alkalinity. Estimate your dose for the 80–120 ppm range in seconds. No signup, US gallons + metric.
Enter your pool volume, your measured Total Alkalinity (TA) in ppm, and your target. Most pools run best at 80–120 ppm; saltwater pools often aim a touch lower, around 60–80 ppm, because the chlorine generator continually pushes pH upward and a lower TA tempers that rise. Test TA and pH together, because the two interact: alkalinity is the reservoir that absorbs acid and resists pH swings, so you generally set alkalinity into range first and let pH settle afterward. To raise TA, the calculator assumes sodium bicarbonate (common baking soda), which lifts alkalinity strongly while barely touching pH. To lower TA, it uses an acid such as muriatic acid, the same chemical used for pH, which is why lowering alkalinity and pH are linked operations. Note where your TA reading sits relative to pH: if pH is also low, raising alkalinity will pull pH up as a side effect, so plan the sequence rather than chasing both numbers at once.
To raise alkalinity, the working figure is about 1.4 lb of sodium bicarbonate per 10,000 gallons to raise TA by 10 ppm. Worked example: a 15,000-gallon pool at 60 ppm, target 100 ppm, needs a 40 ppm rise. That is 4 × 1.4 lb × 1.5 (the volume factor) = 8.4 lb of baking soda — add it in two or three rounds, not all at once. In metric, raising 50,000 liters by 10 ppm takes roughly 0.85 kg of sodium bicarbonate, so a 40 ppm rise needs about 3.4 kg. Lowering alkalinity uses acid: roughly 0.8 quart (about 25 fl oz) of muriatic acid (31.45%) per 10,000 gallons drops TA by about 10 ppm, though this also lowers pH, which you then re-raise by aerating. Always recalculate from a fresh test after each addition rather than trusting one upfront dose.
Alkalinity is the shock absorber for pH: when TA is too low the pH 'bounces' — swinging wildly with every rain shower, chlorine dose, or splash of acid — and you will never hold a stable reading. When TA is too high, pH locks high and resists every correction, breeding cloudy water and scale. Both extremes waste chemicals and frustrate water balance, so getting alkalinity right first makes every later adjustment easier. Add baking soda by broadcasting it slowly across the deep end with the pump running, and avoid dumping a whole bag in one spot where it can cloud the water or sink undissolved. Wait at least 6 hours, ideally overnight, for it to circulate fully before retesting, because an early reading will look low. Lowering alkalinity with acid takes patience: add slowly at a return jet, never mix acid with chlorine, and aerate afterward to lift pH back without re-raising TA. Retest TA and pH together the next day.
For most pools, 80-120 ppm is ideal. For saltwater pools, a slightly lower range of 60-80 ppm is often recommended to help manage pH rise.
Common baking soda (sodium bicarbonate) is the most cost-effective and easiest way to raise Total Alkalinity without significantly affecting pH.
To lower Total Alkalinity, add muriatic acid (or dry acid). Pour it slowly in front of a return jet with the pump running, then let the water circulate; this lowers pH too, so afterward aerate the water to bring pH back up while the alkalinity stays down. Make the change in stages and retest.
Adjust Total Alkalinity first, then pH. Alkalinity acts as a buffer for pH, so getting it into the 80-120 ppm range first makes pH far easier to set and keeps it from drifting. If you chase pH while alkalinity is off, the pH will simply bounce back.
High Total Alkalinity (above about 180 ppm) makes pH stubborn and hard to lower, often leaves the water cloudy, and encourages calcium scale on surfaces and equipment. Lower it gradually with muriatic acid, then re-aerate to recover pH.
If your Alkalinity is too low, the water loses its buffering capacity, causing the pH to swing wildly with every small chemical addition or rain event.
As a rule of thumb, about 1.4 lb of baking soda (sodium bicarbonate) per 10,000 gallons raises Total Alkalinity by roughly 10 ppm — in metric, about 0.85 kg per 50,000 liters. Rather than estimating, enter your pool volume and current and target TA above and the calculator returns the exact amount; then add it in two or three stages with the pump running and retest after a few hours.