Pool Chemicals Calculator

What this pool chemistry calculator does

This calculator is the pool chemistry hub at ToolJutsu — one tool for the four daily-and-weekly doses every pool owner needs to know: chlorine, salt, pH, and alkalinity. Type your pool’s gallons once, pick a mode, enter the target change, and the calculator returns the exact fl oz, lb, or oz of the chemical to add — using the same dose rules pool stores and service techs use. The output also tells you how to add it safely (broadcast vs skimmer, pre-dissolve vs pour, wait times before swimming).

How to use the pool chemistry calculator

1. Paste your pool volume in US gallons. Don’t guess — even a 2,000 gal error pushes shock doses 10 % off. Use the Pool Volume Calculator if you haven’t measured.
2. Pick a mode: Chlorine, Salt, pH or Alkalinity.
3. Enter the target change — how much you want to move the reading. Standard top-ups are: chlorine +2 ppm; salt to 3,200 ppm; pH +0.2; TA +10 ppm. Shock dosing is +10 ppm chlorine.
4. Read the headline number, and read the “Now do” box for the safe-addition steps. Pool chemicals dosed wrong damage equipment far faster than dosing them right damages your wallet.
5. Tap Copy summary to text it to your spouse or paste into a pool-care log.

The right order for pool chemistry

Water chemistry adjustments influence each other. Always work in this order:

1. Total alkalinity (TA) — set first because TA buffers pH. The target band is 80–120 ppm (60–80 ppm for saltwater pools where the SWG nudges pH up naturally).
2. pH — after TA is in band. The target is 7.4–7.6, the range at which chlorine is most active and eyes don’t burn.
3. Calcium hardness — once a season check. Target 200–400 ppm; low calcium dissolves plaster, high calcium scales heaters.
4. Cyanuric acid (CYA, stabiliser) — once a season. Target 30–50 ppm for outdoor pools; CYA shields chlorine from UV but also weakens it, so don’t overshoot.
5. Free chlorine (FC) — the daily reading. Target 1–4 ppm. Use the calculator above to dose the increase.

If you skip the TA step, pH will bounce back to wherever the water “wants” to sit, and your chlorine doses won’t seem to hold. Always TA-then-pH.

Dose rules of thumb (per 10,000 gallons)

Multiply by gallons / 10,000 for your pool size. The calculator does this automatically.

Free chlorine vs combined chlorine

Free chlorine (FC) is the active sanitiser. Combined chlorine (CC) is chlorine bonded to ammonia or organics — it’s a weak sanitiser, irritates eyes, and smells like “pool.” Healthy CC is < 0.5 ppm. When CC climbs above 0.5 ppm, shock the pool to 10 ppm FC to break the chloramines apart at “breakpoint chlorination.” Wait until FC drops to 4 ppm before swimming again.

Why test weekly

Pool chemistry changes faster than most owners realise. UV burns chlorine off at 2–5 ppm per day in summer sun. Heavy rain dilutes salt. Swimmers introduce ammonia (sweat, urine, sunscreen). A weekly test of FC, CC, pH, TA, CYA with a drop-test kit (Taylor K-2006 is the gold standard) catches drift before it becomes algae. Strip tests are fine for daily glance-checks but the reference is the drop kit.

Privacy

This calculator runs in JavaScript on your device. There is no fetch call, no analytics on the dose values you enter, no server-side logging. The page works the same way offline once loaded.