What to add to your pool, and how much.
Free calculators that dose for the bottle you actually own, with chlorine targets set by your stabilizer level. The same math runs in the Pool Calc app.
How much chlorine tonight?
Add
0.6gal
of Liquid chlorine 10%
77 fl oz2.3 L
Raises free chlorine from 2 ppm to 6 ppm in 15,000 gal. Best added at dusk.
- Side effects: Salt +6.6 ppm.
- Pour it slowly in front of a return jet with the pump running.
Check the product label. Strengths vary by brand, so enter the % printed on yours. Add one chemical at a time, into the water, and never mix chemicals.
With CYA at 40 ppm: minimum free chlorine 3 ppm, target 6 ppm, shock level 16 ppm. FC/CYA chart
Calculators
Each one answers a single question with an amount for your product, in US or metric units, and shows its working.
- All-in-one pool calculatorEnter a full test. Get every dose, in the order to add them.
- Chlorine calculatorLiquid chlorine, bleach, cal-hypo, dichlor or trichlor, for your pool.
- Pool volume calculatorGallons or litres for any shape, from length, width and depth.
- pH calculatorAcid to lower pH or soda ash to raise it, using your alkalinity.
- FC/CYA calculatorMinimum, target and shock chlorine for your CYA level.
- Shock (SLAM) calculatorThe shock level from your CYA, and how much product reaches it.
- Alkalinity calculatorBaking soda to raise TA, or acid and aeration to lower it.
- Stabilizer (CYA) calculatorGranular or liquid stabilizer to reach your CYA target.
- Pool salt calculatorPounds, kilograms and bags of salt for your salt cell’s target.
- CSI / LSI calculatorIs your water corrosive or scale forming? CSI and LSI.
- Calcium hardness calculatorCalcium chloride for your surface’s hardness target.
- Drain and refill calculatorHow much water to replace to lower CYA, calcium or salt.
- What will this do?Type an amount of any product and see every change it makes.
Your pool, one test at a time
One pool? Every feature, free. Pool Calc turns a water test into one clear sentence and the doses for your products, then keeps every test and every chemical in a log that backs up to iCloud for free.
Pool Calc for iPhoneComing soon to the App StoreBackyard pool
Lower pH, then add chlorine tonight.
Tested today 8:12 AM
What to add now
Your water
Test water
Your doses
Two additions. Start with acid.
Liquid chlorine 10%
FC 2.0 to 6.0
0.6gal
galfl ozL
Pour slowly in front of a return jet.
After the acid has circulated 30 min.
Check the product label. Strengths vary by brand.
Mark as added
Add first. Retest pH after 30 minutes.
Log
Today 8:12 AM
FC 2.0pH 7.9TA 80
Tue 7:40 PM
FC 4.5pH 7.6
Added 38 fl oz liquid chlorine
Sun 6:05 PM
FC 5.0pH 7.5CYA 40
Fri 7:15 PM
FC 3.0pH 7.7
Added 0.6 gal liquid chlorine
Thu 7:02 PM
FC 4.0pH 7.6CH 320
Added 12 fl oz muriatic acid
Tue 6:48 PM
FC 3.5pH 7.5
Backed up to iCloud 2 min ago
Built for the moment you’re holding the test kit
- Chlorine set by your CYA
- Minimum, target and shock levels move with your stabilizer, the way experienced pool owners run their water.
- Doses for your bottle
- Liquid chlorine, bleach, cal-hypo, dichlor, trichlor, muriatic or dry acid, soda ash, baking soda, borax, calcium, stabilizer, salt and MPS, at the strength on your label.
- One screen per test
- Tap in the values you tested. Anything you skip stays blank in your log, and if a dose needs it (pH doses need alkalinity) the result says what it assumed.
- Safety built in
- Large acid, alkalinity, pH and calcium doses are split into smaller additions, acid and chlorine are never scheduled together, and every dose reminds you to check the label.
- Water balance
- A CSI reading on every result tells you whether the water is etching or scaling.
- Your data stays yours
- No account and no ads. Your log lives on your iPhone and in your own iCloud, and you can export it as CSV.
For pool pros
Plus and Pro add the tools for looking after other people’s pools: Plus for up to 5 pools, Pro for an unlimited route. Both include every tool below.
- Clients and properties
- A card per client with address, phone, email, gate and access notes, and service days. Each pool keeps its own log.
- Today’s route
- The clients due today, in the order you set, ticked off as you finish each stop.
- One screen per stop
- Readings, the doses with “Mark as added”, tasks, photos and notes, all on one screen.
- Branded service report
- A PDF with your logo: readings against target, chemicals added, tasks, photos and the next visit. Send it from your phone by text or email.
- Chemical use and cost
- What you used at each client and what it cost, from the prices on your own product shelf.
- Business profile and logo
- Company name, phone, email, website and license number, printed on every report.
- Client import
- Bring your client list in from a CSV file or from Contacts.
- Bulk CSV export
- Every client’s visits, readings and chemicals in CSV files, ready for your invoicing tool or spreadsheet.
Priced per person, not per pool. No per-pool fees, it works offline, there is no account, and your client data stays in your own iCloud.
For comparison: the web-based pool service software we checked on 27 October 2026 started at $30 to $125 a month for one technician, billed per pool or per user. Pool Calc does not do invoicing, payments or dispatch. It is the chemistry, the log and the report, on your phone.
One pool? Every feature, free.
Free has every pool-care feature for one pool and its attached spa: the full calculator, your whole log, charts, CSI, reminders, widgets and export. Pay only to look after more pools. No weekly plans, no ads.
Free
$0
Every feature, for one pool
- One pool and its attached spa
- Full dose calculator and water balance (CSI)
- Your whole log and every chart
- Unlimited reminders
- Your own product shelf
- PDF and CSV export
- Widgets, themes and app icons
- Free iCloud backup
Pool Calc Plus
$14.99 a year
with a free first week, or $1.99 a month, or $39.99 once
Second homes, small HOAs, a few clients
- Up to 5 pools (a pool and its spa count as one)
- Everything in Free, for every pool
- All the pro tools
- Family Sharing
Pool Calc Pro
$79.99 a year
with a free first month, or $9.99 a month
Service techs and companies
- Unlimited pools
- Everything in Plus
- All the pro tools
- One subscription per technician
Guides
Plain answers to the questions people actually search, each with the calculator built in.
- Cloudy Pool Water: Causes and How to Fix ItCloudy pool? Find which of the five real causes you have (early algae, scaling, filtration, dead algae, debris) and fix it the right way.
- Cyanuric Acid Too High: What It Means and How to Fix ItWhy high CYA forces you to run more chlorine, how to confirm the reading, how much water to replace, and how to stop it creeping back up.
- FC/CYA Chart: How Much Chlorine Your Pool NeedsThe chlorine-to-cyanuric-acid relationship explained, with a chart of minimum and shock (SLAM) chlorine levels for every CYA level.
- Green Pool Water: How to Fix ItWhy pools turn green and how to clear one reliably: test CYA, SLAM with liquid chlorine, brush and filter, and know when you're done.
- How Many Gallons Is My Pool?Pool volume in gallons or litres for rectangle, round, oval, kidney and above-ground pools, plus how to verify it with a simple chemistry check.
- How Much Liquid Chlorine to Add to Your PoolLiquid chlorine doses by pool size and strength, how to pick your target from your CYA level, and how to add it safely.
- How Much Muriatic Acid to Lower pH in a PoolWhy there's no single acid-per-gallon number for pH, how to calculate the right dose from your TA, safe dosing steps, and the dry acid equivalent.
- How Much Shock to Add to a PoolHow much pool shock you really need: set the shock level from your CYA, convert it to liquid chlorine or cal-hypo amounts, and know when shocking is done.
- Pool Alkalinity Too High: How to Lower ItHow to lower total alkalinity in a pool step by step: how much acid per 10 ppm, how aeration brings pH back up, and what TA you should actually aim for.
- Pool pH Too High: Causes, Symptoms and the FixWhy pool pH keeps rising, what high pH actually does, and how to bring it down and keep it down with acid, TA and aeration control.
About the app and this site
Are the calculators on this site the same as the app?
Yes. Both use the same chemistry engine and are tested against the same set of reference results, so a dose here matches the dose in the app.
Do I need an account?
No. There is no sign-up. The app stores your data on your iPhone and backs it up to your own iCloud.
What does the free version include?
Every pool-care feature, for one pool and its attached spa: the full dose calculator, your whole log and every chart, water balance (CSI), unlimited reminders, your own product shelf, PDF and CSV export, widgets and iCloud backup. The pro tools (clients, route, service reports, chemical costs) come with Plus and Pro.
How much are Plus and Pro?
Plus (up to 5 pools) is $1.99 a month, $14.99 a year with a free first week, or $39.99 once. Pro (unlimited) is $9.99 a month, or $79.99 a year with a free first month. Both include the pro tools. There is no weekly plan.
What counts as one pool?
A pool and its attached spa count as one. Archived pools don’t count, so off-season clients cost nothing.
Is it priced per pool?
No. You pay per person, not per pool: one subscription on your Apple Account covers every pool in your plan. Plus can be shared with your family; Pro is one technician per subscription.
What happens if I stop paying?
Nothing is deleted. Your main pool stays fully usable, and any extra pools become view and export only until you subscribe again or archive some.
Which chlorine targets do you use?
Free chlorine follows your cyanuric acid level: a minimum of 7.5% of CYA, a target about 3 ppm above that, and a shock level of 40% of CYA. Salt water pools use 5% and 7.5%.
Is there an Android version?
Not yet. The calculators on this site work in any browser.
Pool Calc for iPhone
One pool? Every feature, free. No account. Free iCloud backup. No ads.
Pool Calc for iPhoneComing soon to the App Store