How Pool Calc works
You test your water, type in the numbers, and Pool Calc tells you exactly what to add and how much.
No chemistry knowledge needed. Here is the whole idea, in plain words.
What you need
- A test kit or test strips Any brand works. Strips are quick; a drop kit gives more exact numbers.
- The chemicals you already have Tell the app what is on your shelf and the strength printed on each label. Every amount is worked out for those bottles.
- Your pool’s size Type in the volume if you know it. If not, pick the shape and enter the measurements, and the app works it out.
- An iPhone No account and no sign-up. Your log stays on your phone and backs up to your own iCloud for free.
Four steps
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Step 1: Test the water
Dip a test strip or run your drop kit, following the instructions that came with it.
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Step 2: Type in the readings
Enter the numbers on one screen. Skip anything you didn’t test.
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Step 3: See what to add
Pool Calc lists what to add, in order, with the amount for the bottle on your shelf. A big dose is split into smaller parts, with the wait between them.
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Step 4: Mark it added
Tap Mark as added once it is in the water. The app logs it and reminds you when to test again.
What the numbers mean
| Reading | What it does | When it’s off |
|---|---|---|
| Free chlorine | The chlorine that’s still working to keep the water clean. | Too low and algae can start to grow. Too high and you wait before swimming. |
| pH | How acidic the water is. 7 is neutral, and pools are kept a little above it. | Too low and the water can etch plaster and attack metal. Too high and chlorine works more slowly and scale can form. |
| Alkalinity | A buffer that keeps pH steady. | Too low and pH swings around. Too high and pH keeps drifting up. |
| Stabilizer (CYA) | Shields chlorine from sunlight so it lasts longer. Pool Calc sets your chlorine target from it. | Too low and the sun burns chlorine off fast. Too high and you need more chlorine for the same effect, and only replacing water brings it down. |
| Calcium | How much calcium is in the water. | Too low and the water can etch plaster and grout. Too high and scale or cloudy water can form. |
Each reading has its own calculator, and the guides explain each fix step by step. To check everything at once, use the all-in-one pool calculator.
Is it free?
Yes, for one pool. Free has every feature for one pool and its attached spa. Plus and Pro are for people with more pools, and add the tools for looking after other people’s pools.
Free
$0
Every feature, for one pool
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
Pool Calc Pro
$79.99 a year
with a free first month, or $9.99 a month
Service techs and companies
Safety
Calculators and guides are for information; doses are estimates from your readings. Always read and follow the label of every product, add chemicals one at a time, and never mix them.
Questions people ask first
Do I need to know chemistry?
No. You type in the numbers from your test and Pool Calc does the math. Each result tells you what to add, how much, and why, in plain words.
Does it work with my test strips?
Yes, with any brand. Choose test strips in the app, then pick the nearest value on the color chart that came with them. A drop kit gives more exact numbers, especially for stabilizer.
What if I use bleach?
That works. Choose household bleach and enter the strength printed on the label, for example 6% or 8.25%. Use plain unscented bleach only. Pool Calc works out the amount for that strength.
Does it work offline?
Yes. Everything runs on your iPhone, so you can test and dose with no signal. Your log backs up to your own iCloud when you are back online.
Can I try it before I get the app?
Yes. The calculators on this site use the same math as the app. Start with the chlorine calculator.