Pool Charm is a pool chemistry calculator and reference guide for homeowners and pool pros. Enter your test readings and it gives you a clear, step-by-step dosing plan — with the reasoning behind every step — so you actually understand your water instead of just following numbers.
It works fully offline, installs to your home screen like a real app, and keeps everything on your device.
Dosing that accounts for the whole picture. It doesn't just say "add X." It works through how your chemicals actually interact — CYA changes how much chlorine you really need, acid pulls alkalinity down along with pH, cal hypo adds calcium, dichlor adds stabilizer — and it orders the steps so you don't overshoot or chase your tail.
It teaches you while you calculate. Every recommendation explains what it's doing and why. Pair that with the built-in Spellbook and you can go as deep as you want — it's a calculator and a pool-chemistry guide in one.
Genuinely easy to use. Punch in your readings and get exact amounts, how-to-add steps, safety notes, and when to retest. No account, no setup hoops, nothing to sign up for.
The Calculator
- FC, pH, total alkalinity, CYA, calcium hardness, combined chlorine, salt
- CYA-aware chlorine targeting (not just a fixed 3–5 ppm)
- Algae & slime shock plans (green, pea soup, mustard, black, pink slime, biofilm)
- Ammonia breakpoint chlorination
- Phosphate remover dosing
- Step-by-step instructions with safety warnings and retest timing
- Trichlor / liquid / salt cell / manual sanitizer support
The Spellbook
- 9 chapters of plain-English pool chemistry — chemicals, filtration, algae, stains, salt systems, problem water, and more
- Section search across every chapter
- Reads fully offline, so it's there with you poolside
History & Profile
- Save your pool profile once — gallons, surface type, sanitizer preference
- Log readings over time and watch FC, pH, and alkalinity trends on a chart
- Back up and restore your data to a file — move it between devices anytime
- Everything stays on your device — nothing is uploaded
Pool Charm is a Progressive Web App — it installs straight from your browser, no app store required.
iPhone / iPad: Open in Safari → Share ⬆ → Add to Home Screen
Android: Open in Chrome → Menu ⋮ → Add to Home Screen
Desktop: Click the install icon in Chrome or Edge's address bar
Once installed it launches full-screen like a native app and works with no internet connection.
Pool Charm is free. To keep it that way:
- 📢 Small ads sit in a few unobtrusive spots — no pop-ups, no video.
- 🧪 Affiliate link — if you're buying pool chemicals anyway, using the Shop link costs you nothing extra and sends a small commission my way. Genuinely appreciated.
Pool Charm provides chemistry guidance for informational purposes only — not professional advice. Pool chemicals are hazardous. Always read product labels, wear eye protection, and never mix chemicals. Use at your own risk. Governed by the laws of the State of Kansas.
🌊 Open the app → poolcharm.app
All dosing approximate. Always retest after dosing.