Pool water chemistry calculators: which one to use, and in what order

If you keep one pool or forty, the chemistry is the same arithmetic repeated: a target, a current reading, a product strength, and a volume of water. The hard part is rarely the math — it is knowing which lever to pull first and which tool does it. The calculators below are grouped the way the work actually happens, not alphabetically, so you can land on the right one in a few clicks.

A note on what this page is and is not. It is a map to the math. It deliberately does not print target levels — no “keep your chlorine here” or “your stabilizer should be that.” Those numbers belong to your test kit, the product label, and your training, and they change with your pool, your sanitizer system, and your bather load. Each calculator asks you for the target and the product you actually bought, then does the conversion. The job of this hub is only to send you to the right one.

1. Start here: measure the water

Every dose on every page below is an amount of chemical per gallon. Get the gallons wrong and you scale every later dose wrong in the same direction — a pool you think is 15,000 gallons but is really 20,000 will be under-treated by a quarter no matter how careful the rest of your math is. So this is the one number worth getting right once and reusing everywhere.

The volume calculator handles rectangles, rounds, ovals, kidneys, and freeform shapes, and averages a shallow and deep end for you. Write the result down; you will paste it into nearly every other tool on this page.

2. Balance the water

Four readings move together and decide whether your water is comfortable, clear, and easy on the surface and equipment: total alkalinity, pH, calcium hardness, and cyanuric acid. They interact — alkalinity buffers pH, calcium and pH and alkalinity together decide whether water is scaling or corrosive — which is why pool keepers fold them into a single saturation index rather than chasing each one alone. Each tool below sizes the dose to move one reading from where it is to where you want it; the LSI tool reads the whole set at once.

• Total Alkalinity calculator — baking soda to raise alkalinity, or acid to lower it, from your current and target ppm.
• Muriatic Acid Dose calculator — how much muriatic acid to bring pH or alkalinity down, sized to the acid strength you actually bought.
• Calcium Hardness calculator — the purity-corrected calcium chloride dose to raise hardness, or the drain-and-refill percentage to lower it.
• Cyanuric Acid (Stabilizer) calculator — stabilizer to add to raise CYA, or the dilution percentage to lower it.
• LSI / Langelier Saturation Index calculator — rolls pH, temperature, alkalinity, calcium, CYA, and TDS into one balanced / corrosive / scaling verdict, with the full factor breakdown.

If you would rather enter every current-versus-target reading once and get a single ordered dose sheet — including the correct add-order, since some chemicals should not go in back to back — the all-in-one dosing tool does the whole balance set in one pass.

3. Sanitize: chlorine and the stabilizer that protects it

Chlorine is the sanitizer that keeps the water safe to swim in, and it cannot be judged in isolation from cyanuric acid. Stabilizer shields free chlorine from being burned off by the sun’s UV, but the more stabilizer in the water, the more free chlorine it takes to do the same work — so the right chlorine level is always a function of your CYA, not a fixed figure. That is the relationship these three tools are built around.

• Pool Chlorine Dose calculator — the exact dose in pourable units for liquid, cal-hypo, dichlor, trichlor, or bleach, with the CYA, calcium, or pH each one also adds flagged inline.
• FC/CYA Target Ratio calculator — enter your stabilizer level and pool type for the minimum, target, and SLAM free-chlorine levels and your live ratio.
• Chlorine Type Cost-Per-PPM Comparator — ranks liquid, cal-hypo, trichlor, and dichlor by the true cost to raise free chlorine, with the side-effect each one hides.

The choice of chlorine type is a chemistry decision as much as a cost one: trichlor and dichlor are stabilized chlorines, so they add cyanuric acid every time you use them; cal-hypo adds calcium; liquid chlorine and bleach add neither but are weaker by volume. The dose calculator flags those side effects so a convenient product does not quietly push another reading out of range over a season.

4. Fix a problem: cloudy, smelly, or green water

When the water is balanced and sanitized, most problems are a chlorine-demand event — something is consuming chlorine faster than the routine dose replaces it. These three tools size the corrective dose for the three most common versions of that.

• Pool Shock calculator — pick the chemical, its strength, and a target (breakpoint, a reason preset, or a custom level) and read the dose in pounds, ounces, or gallons.
• Breakpoint Chlorination calculator — how much shock to push free chlorine past breakpoint and destroy the chloramines behind the harsh “chlorine smell.”
• Green Pool / Algae Recovery calculator — the CYA-aware shock target for an algae bloom and how much chlorine to pour now, plus the exit test that tells you it has cleared.

These overlap on purpose — a green pool, a chloramine smell, and a cloudy-after-a-party pool are different demands on the same lever, chlorine — so pick the tool by the symptom in front of you. The green-pool tool sets a sustained, elevated free-chlorine target (the method many pool keepers call a SLAM) and is the right one only when there is a visible algae bloom; for a faint smell with otherwise clear water, breakpoint is the cheaper, smaller correction.

5. When the only fix is replacing water

Some readings only go one way by adding chemicals. Cyanuric acid, calcium hardness, salt, and total dissolved solids climb over a season and there is nothing you can pour in to bring them back down — the only lever is replacing water, and dilution is just arithmetic on how much.

• CYA Drain / Dilution calculator — the drain-and-refill percentage and the gallons needed to lower CYA, calcium, salt, or TDS to a target, with a staged plan for large drains.

This is the tool to reach for when the cyanuric acid or calcium tool above tells you the level is too high: it answers the follow-up question — how much water do I actually have to swap out — instead of leaving you to guess.

6. Saltwater pools

A saltwater pool is still a chlorine pool; it just makes its own chlorine by running dissolved salt through a salt cell. That changes two questions from the start of the route: how much salt the water needs, and whether the cell is sized to keep up.

• Pool Salt calculator — pounds and bags of salt to hit your cell’s target, or the gallons to drain when salt is too high.
• Salt Cell Sizing calculator — the recommended cell class and minimum rating for your pool, with an oversize factor and a run-percent longevity check.

Everything in sections 2 through 5 still applies to a salt pool — balance, stabilizer, and shock are the same — so use these two alongside the rest, not instead of them.

7. For the route: what the chemistry costs you

If you keep pools for a living, every dose above is also a line item. A residential pool you service on a recurring billing plan earns the same flat monthly fee whether the water behaved or fought you all month, so the chemicals you pour are your cost of goods sold — and the gap between that flat fee and your real chemical-and-time cost is the gross margin the route lives on. Two of the tools above double as cost tools, and one more closes the loop on price.

• Pool Chemical Cost & Margin calculator — turns bulk chemical buys into a true cost per visit, subtracts your flat rate, and flags the margin left.
• Chlorine Type Cost-Per-PPM Comparator — the cheapest way to raise free chlorine for your pool, side effects included, so you are not over-paying per ppm out of habit.
• Pool Service Price calculator — builds a profitable monthly price per pool from an itemized cost stack, so the flat fee actually covers the chemistry.

Run tight enough route density and your drive time per stop drops, which is often a bigger lever on a pool route’s profit than the chemicals themselves — but that is the business side of the trade, and it is where the free calculators end and a system to run the route begins.

How to use this map

Work top to bottom the first time and the order takes care of itself: measure the volume once, balance the four readings that move together, sanitize with chlorine matched to your stabilizer, fix the specific problem in front of you, drain only what nothing else can lower, and — if it is a salt pool — size the salt and the cell. After that you are not reading a guide anymore; you are reaching straight for the one calculator the day calls for. Bookmark this page as the index, and let each tool own the number it was built to compute.