Pool Calculator
Free all-in-one pool calculator — get exact dosing for chlorine, pH, alkalinity, calcium hardness and salt for your pool volume, all on one screen. Based on TFP/PoolMath.
Enter your pool volume, then tap a key — Cl₂ · pH · TA · Ca · Salt — and spin the dials to your test reading. It tells you exactly how much of each chemical to add. No sign-up, free.
How to use the pool calculator
- Enter your pool volume in gallons. Not sure? Calculate it here.
- Pick chlorine type (liquid, cal-hypo, dichlor, trichlor) and your CYA — the calculator sets a recommended Min FC at ~10% of CYA. That's a little above Trouble Free Pool's bare minimum (~7.5% of CYA for a regular pool, ~5% for salt), to give you a cushion; your daily target can sit a bit higher still. Keep your free chlorine at or above the Min FC.
- Tap a function key on the right of the screen to switch between Chlorine, pH, Alkalinity, Calcium, and Salt.
- Spin the "Now" dial to your test-kit reading. The display shows exactly how much to add — switch units (oz, lb, gallons, mL) right on the screen.
- Add one chemical at a time, with the pump running, and retest before the next.
Doses use the same TFP/PoolMath effect factors as our individual chlorine, pH, alkalinity, calcium and salt calculators — this just puts them on one screen.
Ideal pool chemistry ranges
| Level | Ideal range | Notes |
|---|---|---|
| Free Chlorine (FC) | ~10% of CYA (minimum) | Keep at or above this; never below 7.5% of CYA. Above 10 ppm = wait to swim. |
| pH | 7.4 – 7.6 | Lower with muriatic acid, raise with soda ash. |
| Total Alkalinity (TA) | 80 – 120 ppm (50 – 90 for SWG) | Buffers pH. Salt pools run lower. |
| Calcium Hardness (CH) | 250 – 400 ppm (plaster) | Vinyl/fiberglass less critical; can't be lowered chemically. |
| Cyanuric Acid (CYA) | 30 – 50 ppm (70 – 80 SWG) | Protects chlorine from sunlight. |
| Salt (SWG only) | ~3,000 – 3,500 ppm | Check your generator's spec. |
Frequently asked questions
How much chlorine do I add to my pool?
It depends on your pool volume, current free chlorine, and CYA. Enter your volume, pick your chlorine type, set your CYA, and spin the Current FC dial — the calculator shows the exact dose. As a rule of thumb, keep free chlorine at a minimum of about 10% of your CYA level (a touch higher gives you cushion between doses).
How much muriatic acid to lower pH or alkalinity?
To lower pH, the calculator doses muriatic acid directly. To lower total alkalinity, it estimates the total acid needed, but you add it in stages: lower pH to ~7.2, aerate the water to bring pH back up, retest, and repeat.
How much baking soda raises alkalinity?
Roughly 1.4 lb of baking soda per 10,000 gallons raises total alkalinity about 10 ppm. Set your current and target TA and the calculator does the math for your exact volume.
What chlorine level is unsafe to swim?
Most health codes cap free chlorine at about 10 ppm for swimming. Above that, wait for it to drop — sunlight burns it off (faster with low CYA), or use a chlorine neutralizer.
Is this pool calculator free?
Yes — every calculator on Pool Repair Question is free with no sign-up.