Pool Total Alkalinity Calculator
Calculate the baking soda to raise total alkalinity (TA) to your target, or an estimate of the acid to lower it. Enter your pool volume and current and target TA to get the dose.
Calculator
Add 4.50 lb of baking soda to raise total alkalinity from 80 to 100 ppm.
Total alkalinity (TA) is the water’s buffering capacity — its resistance to sudden pH swings. Keep it in a sensible band (commonly 80-120 ppm) and pH becomes far easier to hold steady. Too low and pH bounces around unpredictably; too high and pH tends to creep upward and scale can form.
You raise alkalinity with baking soda (sodium bicarbonate), which is inexpensive and gentle. You lower it with acid, exactly as for pH — and because that also drives pH down, lowering TA is treated here as an estimate.
Formula
To raise TA, the tool uses the standard increment for baking soda:
baking soda (lb) = 1.5 × (Δppm ÷ 10) × (gallons ÷ 10,000)
which reflects the well-known rule that about 1.5 lb of baking soda raises 10,000 gallons by 10 ppm. Here Δppm = target TA − current TA. To lower TA, the tool estimates muriatic acid (the same acid used for pH), and flags the result as an estimate because pH and alkalinity move together and the water should be aerated and re-tested as you go.
Worked example
A 15,000-gallon pool at 80 ppm TA, targeting 100 ppm:
- Δppm = 100 − 80 = 20 ppm.
- baking soda = 1.5 × (20 ÷ 10) × (15,000 ÷ 10,000) = 1.5 × 2 × 1.5 = 4.5 lb.
- Broadcast it over the pool with the pump running, circulate a full turnover, then re-test.
Raising a larger 20,000-gallon pool by the same 20 ppm would take 1.5 × 2 × 2 = 6 lb.
Balancing alkalinity and pH
Baking soda dissolves readily; broadcast it across the surface with the pump on and give it a full turnover before re-testing. Adjust alkalinity before you fine-tune pH, because a stable TA makes pH much easier to hold. If TA is high and pH keeps climbing, lowering alkalinity with acid (and aerating to bring pH back up) is the classic fix.
Very high alkalinity is often the hidden reason a pool “eats” acid — you keep adding acid to chase pH, which lowers TA a little each time until it finally settles. Because acid affects both numbers, this calculator gives the lowering step as an estimate and expects you to re-test. On the raising side, the baking-soda math is exact and evergreen.
Because the buffering effect is what makes pH stable, think of alkalinity as the foundation and pH as the finish: get TA into its band, then set pH, and both tend to stay put far longer. If you routinely test only pH you can miss a slow alkalinity drift that is quietly driving those pH swings, so include total alkalinity in your regular testing and let this calculator size any correction.
Frequently asked questions
How much baking soda to raise alkalinity?
About 1.5 lb of baking soda raises 10,000 gallons by 10 ppm of total alkalinity. For a 20 ppm rise in a 15,000-gallon pool that works out to 4.5 lb. The calculator scales it to your exact volume and target.
What total alkalinity should a pool have?
A common range is 80-120 ppm, which buffers pH nicely for most pools. Plaster and salt pools sometimes aim toward the lower end. Follow your test kit and the product guidance; this tool sizes the dose only.
How do I lower total alkalinity?
Add muriatic acid, ideally in one spot with little circulation, then aerate the water to bring pH back up while TA stays lower. It is an estimate and usually takes a few rounds — add some acid, aerate, re-test, repeat.
Should I fix alkalinity or pH first?
Adjust alkalinity first. Because TA buffers pH, getting alkalinity into range makes pH stable and predictable, so your pH adjustments actually hold instead of drifting back.
Why does my pool keep needing acid?
Usually high total alkalinity. It acts as a pH engine, pushing pH up so you keep adding acid. Lowering TA into range (then aerating) settles the cycle. Fresh plaster and certain fill water can also raise alkalinity over time.