Pool Alkalinity Dosing Calculator
Enter your pool volume and current and target total alkalinity to get the exact dose. Raising takes 1.5 lbs of baking soda per 10,000 gallons per 10 ppm — 6 lbs to go from 60 to 100. Lowering takes acid, and this schedules it in safe rounds so pH does not crash.
Which way you are going changes the whole job. Raising alkalinity is one measured scoop of baking soda and a wait — the amount follows straight from your pool size and how many ppm you are short. Lowering it is a project, because the only thing that removes alkalinity is acid, and acid takes pH down with it. That is why the lowering side asks for your pH too: it decides how much can safely come out per round, and how many rounds of dose-and-aerate the correction really takes.
Pool volume
How many gallons your pool holds. Typical sizes: a small above-ground pool is about 10,000, a standard in-ground pool 15,000–20,000, a large one 30,000 or more. Length times width times average depth in feet, times 7.5, is close enough for a rectangular pool.
Current total alkalinity
What your test kit reads now, in ppm. Readings under 60 are very low, 80–120 is balanced, and 150 or more is high. Test strips give you the range; a liquid reagent kit is worth using for a big correction, because the dose is only as good as this number.
Target total alkalinity
Where you want to land. Most guidance puts the band at 80–120 ppm, and 100 is a comfortable middle; saltwater and high-pH-drift pools often run 80–90. Some product labels recommend 100–150 instead, so if your pool has always been happy at a particular number, use that.
Baking soda to add today
5.1 lbs
Then wait 6 hours and retest. If alkalinity is still below 100, add the remaining 1.7 lbs.
Three-quarters now, the rest only after a retest
Broadcast 5.1 lbs across the surface with the pump running, wait 6 hours, then retest both alkalinity and pH. The label dose rounds high on purpose and pH climbs along with alkalinity, so this first addition often lands you at target — add the remaining 1.7 lbs only if the test still says you're short.
Raising uses the sodium bicarbonate label dose of 1.5 lbs per 10,000 gallons per 10 ppm, reproduces the published dose table exactly, and stages it — three-quarters first, retest after six hours, the rest only if needed — because the label rounds high on purpose. Lowering computes the acid from equivalents — the amount is fixed by chemistry — while the round count comes from solving the carbonate balance for the largest alkalinity drop that keeps pH at or above 7.0, capped at 20 ppm per day. Round counts assume you aerate pH back up between rounds, so treat them as a plan rather than a promise, and retest before every addition. If your pool is heavily stabilized, part of your alkalinity reading is cyanuric acid rather than carbonate. 2026 figures.
💡About this calculator▼
Total alkalinity is the only pool reading where the two directions are completely different jobs, and treating them as one is where people get into trouble.
Going up is easy. Baking soda raises alkalinity and almost nothing else. The amount follows straight from your pool size and how many ppm you are short, you broadcast it with the pump running, and you retest in four to six hours. That is the whole procedure.
Going down is a project. Nothing removes alkalinity except acid, and acid takes pH down along with it — you cannot touch one without moving the other. A pool sitting at 180 ppm that wants to be at 100 needs enough acid to strip 80 ppm of buffer, and dumping that in at once would take pH somewhere in the low sixes: etched plaster, dissolved grout, corroded heater parts. The correct method is rounds. Remove a slice of alkalinity, then aerate — run a waterfall, angle the return jets up to break the surface — which drives off carbon dioxide and lifts pH back up without putting alkalinity back. That is the one lever that separates the two readings, and it is what makes a big reduction possible at all.
So this calculator does two different things depending on which way you point it. Ask it to raise, and you get a weight and a wait. Ask it to lower, and it also asks your current pH — because that is what decides how much alkalinity can safely come out per round, and therefore how many rounds you are actually signing up for.
Raising: one constant, scaled twice. Sodium bicarbonate — sold as alkalinity increaser, chemically identical to grocery baking soda — raises total alkalinity by 10 ppm for every 1.5 lbs per 10,000 gallons. Multiply that by how many times 10,000 gallons your pool is, and by how many times 10 ppm you are short. A 10,000-gallon pool going from 60 to 100 ppm needs 6 lbs; from 80 to 100, 3 lbs; from a badly depleted 40 up to 100, 9 lbs. But the total is never one addition. The label dose rounds about 7 percent high on purpose, and pH climbs along with alkalinity, so the calculator stages it the way the manufacturer does: three-quarters first, wait six hours with the pump running, retest both numbers, and add the rest only if the test still calls for it — it often won't. Below 60 ppm the correction goes in three additions over a day or two, and never more than two additions in a day.
Lowering, part one: how much acid. This part is fixed chemistry and does not care about your pH. Removing 10 ppm of alkalinity from 10,000 gallons takes about 25 fl oz of full-strength 31.45% muriatic acid. If you are using the low-fume 14.5% version you need about 2.3 times that, and dry acid (granular sodium bisulfate) runs about 1.5 times the fluid-ounce figure, weighed in ounces.
Lowering, part two: how fast you're allowed to. This part is entirely about pH. Every ounce of acid pushes pH down as it eats alkalinity, and pH must not go below 7.0, where water turns corrosive to plaster, grout and metal. How far it falls for a given alkalinity drop depends on where pH started and how much buffer is left, so the calculator solves for the biggest drop that stays above the floor, then applies the industry ceiling of no more than 20 ppm of alkalinity in a single day on top of it. Whichever limit is tighter sets the round size.
Between rounds, you aerate. Aeration offgasses carbon dioxide, which raises pH and leaves alkalinity alone. Alternate acid and aeration and alkalinity walks down while pH stays in range. Note that later rounds get smaller: as alkalinity falls there is less buffer, so pH drops faster per ounce of acid.
📐How it's calculated▼
Raising: pounds = 1.5 × (gallons ÷ 10,000) × (ppm needed ÷ 10). A 15,000-gallon pool reading 70 ppm that wants 100 ppm is short 30 ppm: 1.5 × 1.5 × 3 = 6.8 lbs of baking soda. The published dose reference for a 10,000-gallon pool lists 9 lbs to go from 40 to 100, 6 lbs from 60, 4.5 lbs from 70, and 3 lbs from 80 — this calculator reproduces every one of those figures, and doubles them for a 20,000-gallon pool exactly as the same table does.
Lowering, the amount: total alkalinity converts to equivalents by dividing by 50.043, the equivalent weight of calcium carbonate, and each equivalent of alkalinity needs one equivalent of hydrogen chloride to neutralise it. Full-strength acid carries 0.365 grams of hydrogen chloride per millilitre, which works out to 25.6 fl oz per 10,000 gallons per 10 ppm — matching the roughly 25 fl oz the published chart gives.
Lowering, the schedule: pH equals 6.35 plus the base-10 logarithm of the bicarbonate-to-carbonic-acid ratio. Acid moves bicarbonate into carbonic acid, so setting that equation to pH 7.0 and solving for the amount gives the largest alkalinity drop the pool can take before it goes corrosive.
Worked example. A 20,000-gallon pool reads 180 ppm alkalinity and pH 7.6, and wants 100 ppm. The total acid is 8 × 51.1 = 409 fl oz, about 3.2 gallons of full-strength muriatic. But at pH 7.6 and 180 ppm, the largest drop that keeps pH at or above 7.0 is about 25 ppm, so the 20 ppm daily ceiling is the binding limit. Round one is therefore 20 ppm — 102 fl oz — which lands pH at about 7.1. Aerate back up, retest, repeat: five rounds in total, each smaller than the last as the buffer thins out.
Target ranges. Most guidance puts total alkalinity at 80–120 ppm, though some product labels recommend 100–150. The CDC recommends pool pH of 7.0–7.8.
📎Sources:CDC Healthy Swimming — Home Pool and Hot Tub Water Treatment and Testing,Orenda Technologies — How to Lower Alkalinity in a Pool,PoolChem Tracker — How to Raise Pool Alkalinity (baking soda dose table),Arm & Hammer — Maintain Your Pool with Baking Soda (manufacturer dosing and staging guidance)
🔍Finding your inputs▼
Pool volume: How many gallons your pool holds. Length times width times average depth in feet, times 7.5, gets you close for a rectangular pool. Every dose on this page scales directly with volume, so an error here is an error in the answer by the same proportion.
Current total alkalinity: Your reading in ppm right now. Test strips are fine for spotting that something is off, but a liquid reagent kit is worth using before a large correction, because everything downstream is built on this number. Retest after heavy rain — rain is acidic and pulls alkalinity down over a season.
Target total alkalinity: Where you want to land. The commonly cited band is 80 to 120 ppm, and 100 sits comfortably in the middle. Some alkalinity increaser labels recommend 100 to 150 instead, so if your pool has historically been stable at a particular number, use that rather than moving it for its own sake. The calculator works out the direction from this number against your current reading — set it higher and you get baking soda, lower and you get an acid schedule.
Current pH reading: Only asked when you are lowering, and ignored entirely when you are raising. On the lowering path it does real work: acid drags pH down along with alkalinity, so where pH starts decides how much alkalinity can safely come out per round before hitting the 7.0 floor. Starting at 7.8 buys you a much bigger round than starting at 7.2. If pH is already at 7.0, there is no safe dose at all until you aerate first, and the calculator will say so instead of handing you a number.
Which acid you're using: Also only asked when lowering. Read the jug rather than assuming: full-strength muriatic acid is labelled 31.45% or 20 Baumé, and the low-fume version is 14.5% or 10 Baumé and needs more than twice as much for the same job. Dry acid is granular sodium bisulfate and is weighed on a scale rather than poured, so the calculator switches to ounces by weight when you pick it.
⚠️Special situations▼
My alkalinity is high and my pH is high — which do I fix first?
Alkalinity, and it usually fixes pH on the way. High alkalinity is very often the reason pH keeps climbing back after every acid dose: the more buffer in the water, the more carbon dioxide it holds and releases, and the harder pH is pushed upward. Chase pH on its own and you will be back next week. Bring alkalinity into the 80 to 120 range using the schedule here, and pH generally becomes stable enough to hold with far less acid. The one exception is if pH is already at or below 7.0, in which case aerate to raise it before you add any acid at all.
Can I use grocery-store baking soda instead of pool alkalinity increaser?
Yes. Alkalinity increaser sold for pools is sodium bicarbonate, and so is baking soda — the ingredient label on the pool product is typically 100% sodium bicarbonate. The dose is identical: 1.5 lbs per 10,000 gallons per 10 ppm. The only practical difference is packaging and price per pound, and for larger pools the 25 or 50 lb pool bags usually work out cheaper than boxes. Do not confuse it with soda ash (sodium carbonate), which is a different chemical that raises pH primarily and alkalinity only a little — that is the one to reach for when pH is low but alkalinity is already fine.
The calculator says five rounds — can I speed it up by adding more at once?
No, and the limit is the pool surface rather than the chemistry. Alkalinity should not come down more than 20 ppm in a day, and beyond that your starting pH sets its own ceiling: take too much buffer at once and pH goes below 7.0 on the way to the target, which etches plaster, dissolves grout, and corrodes metal fittings and heater components. What actually shortens the job is aerating harder between rounds — running a waterfall or spa jets, or aiming the returns up to break the surface — because that recovers pH faster and lets the next round start sooner. You cannot take acid back out once it is in.
I raised alkalinity and now my pH is too high
That is expected — baking soda raises alkalinity primarily and pH modestly, which is exactly why it is the right choice when both readings are low. If pH has overshot but alkalinity has landed where you want it, do not reach for acid immediately, because acid will pull the alkalinity you just paid for back down with it. Wait and retest first; pH often settles on its own. If it is still high after a day, use a small acid dose sized for the pH move rather than the alkalinity move, and expect to lose a few ppm of alkalinity in the process.
❓Common questions▼
How much baking soda do I need to raise my pool alkalinity?
The rate is 1.5 lbs per 10,000 gallons for every 10 ppm you want to gain, and it scales linearly in both directions. A 10,000-gallon pool going from 60 to 100 ppm needs 6 lbs; from 80 to 100, 3 lbs; from 40 to 100, 9 lbs. Double all of those for a 20,000-gallon pool. The headline is today's first addition, about three-quarters of the total; the total sits in the row below and is only for the retest to confirm. Broadcast it across the surface with the pump running rather than dumping it in one spot, wait six hours, then retest both alkalinity and pH before adding any more — baking soda dissolves slowly, an early test reads low, and the label dose rounds high, so the first addition often finishes the job.
What is the ideal total alkalinity for a pool?
Most guidance points at 80 to 120 ppm, with 100 a comfortable middle. Below 80 there is not enough buffer, and pH starts swinging on you with every rain shower or dose of chlorine. Above about 120 the opposite happens: pH gets locked high and drifts back up no matter how much acid you add, and above 150 you also start seeing cloudy water and scale on tile, the heater and a salt cell. Worth knowing that published targets genuinely differ — some product labels recommend 100 to 150 — so if your pool has been stable at a particular number for years, that number is not wrong.
How do I lower alkalinity without lowering pH?
Not in one step, because acid always takes both down together. The technique is to alternate. Add acid, which lowers alkalinity and pH; then aerate the pool, which drives off carbon dioxide and raises pH back up while leaving alkalinity exactly where the acid left it. Run a waterfall or spillover, turn on spa jets, or angle the return jets upward so they break the surface. Repeat that cycle and alkalinity walks down in steps while pH keeps returning to a safe level. Aeration is the only common lever that moves pH without moving alkalinity, which is what makes a large reduction possible at all.
Why does my pool need so much acid to lower alkalinity?
Because you are neutralising the entire buffer, not just nudging a reading. Removing 10 ppm of alkalinity from 10,000 gallons takes about 25 fl oz of full-strength 31.45% muriatic acid, so a 20,000-gallon pool coming down from 180 to 100 ppm needs roughly 409 fl oz — about 3.2 gallons in total. That figure is fixed by chemistry and does not change with your pH. What your pH does change is how fast you are allowed to add it: spread across five rounds with aeration between, that same 3.2 gallons is routine, whereas poured at once it would take pH into the low sixes and damage the pool.
How long should I wait between doses?
For baking soda, four to six hours with the pump circulating before you retest, and you can safely do two additions in a day if a large correction calls for it. For acid when lowering alkalinity, work in daily rounds: add, circulate, aerate to recover pH, and retest both alkalinity and pH the next day before the next round. Do not work from the original schedule without retesting — the numbers move together, and the safe size of each round depends on where both readings actually are, not where the first calculation predicted they would be.
🔗 Related Calculators
Muriatic Acid Dosing Calculator
Enter your pool volume, pH reading, and total alkalinity to get the exact muriatic acid dose in fluid ounces. A 15,000-gallon pool at pH 8.0 needs about 17 fl oz to reach 7.5 at 100 ppm alkalinity — but 26 fl oz at 150 ppm. Handles 31.45% and 14.5% acid and dry acid.
Calcium Hardness Dosing Calculator
Enter your pool size, surface, and calcium hardness readings to get the calcium chloride dose, split into safe additions, or the share of water to drain and refill when calcium is too high. Uses label rates: 1.25 lbs of flake per 10,000 gallons per 10 ppm, never more than 10 lbs per 10,000 gallons at once.
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Calculate your pool volume in gallons for rectangular, oval, round, and kidney-shaped pools. Enter length, width, and depth to get an accurate gallon count for chemical dosing.
Cyanuric Acid Dosing Calculator
Calculate exactly how much cyanuric acid (pool stabilizer) to add to raise CYA to your target level — or how many gallons to drain if CYA is too high. Includes minimum free chlorine guidance.