Chlorly: Pool Water Calculator

Chlorly turns a pool or hot-tub water test into exact amounts of the products you already own — in the right order, with how long to wait between them. No brand to buy, no guessing.

ENTER YOUR TEST
Free chlorine, combined chlorine, pH, total alkalinity, calcium hardness, CYA (stabiliser), salt, borates and temperature. Leave out what you didn't test. US units (gallons, °F) or metric (litres, °C).

TARGETS THAT FIT YOUR POOL
• Free chlorine follows your CYA level (the FC/CYA method), including the shock (SLAM) level
• pH 7.2–7.8, alkalinity by sanitiser, calcium by surface (plaster, vinyl, fibreglass)
• Salt targets for salt-water generators, bromine for spas
• Every reading gets a colour and a plain-English explanation

EXACT DOSES FOR YOUR PRODUCTS
Tell Chlorly what is on your shelf and the strength on each label: liquid chlorine (10 or 12.5 %), bleach, cal-hypo, dichlor, trichlor, muriatic acid (31.45 % or 14.5 %), dry acid, baking soda, soda ash, calcium chloride, stabiliser, salt and borax. Chlorly works out how much of WHICH product to add, in fl oz, gallons, pounds, millilitres or grams, and shows what else each one changes — acid lowers alkalinity, dichlor adds CYA, cal-hypo adds calcium.
The steps come in a safe order with wait times, and a clear reminder to add one chemical at a time and never mix them.

THE CHEMISTRY, SHOWN
pH corrections come from an acid/base equilibrium model that accounts for alkalinity, CYA and borates, not a rough table. The saturation index (CSI, the Langelier index adapted for pools) tells you whether your water is etching plaster or laying down scale. Every formula is unit-tested against published reference values.

POOL VOLUME CALCULATOR
Rectangle, round, oval, kidney or freeform, with shallow and deep ends — or type the volume in.

LOG, CHARTS AND REMINDERS
Keep every test and see each reading over time against its target band. Log filter cleans, backwashes and shocks. Get a reminder when the next test is due.

FREE
One pool or spa, every result and dosing plan, the last 10 tests and the maintenance log, with a small banner advert.

CHLORLY PRO — one payment, no subscription
• Unlimited pools and spas
• Full test history with charts
• Saturation index (CSI)
• Test reminders
• CSV and PDF water reports
• No adverts

Your tests stay on your phone: no account, no cloud. The only third-party code is Google AdMob for the free version's banner, shown after you choose your consent.

Chlorly is not affiliated with any chemical brand. Amounts are estimates from home test readings — always follow the product label and retest after adding chemicals.