Chlorine Type Cost-Per-PPM Comparator

Sticker price lies: a cheap jug of weak liquid and a pricey bucket of strong tablets don't deliver the same chlorine. We normalize every product to the honest unit — cost to raise free chlorine by 1 ppm in your pool — then rank cheapest first.

Step A — cost per lb of AVAILABLE chlorine
  Liquid:  pricePerGal / lbPerGal / (strength% / 100)
           lbPerGal = 9.7 (≥10% strength) or 9.0 (~6% household bleach)
  Dry:     pricePerLb × (100 / strength%)

Step B — scale to your pool
  costPerPpm      = costPerLbAvail × 0.00834 × (volume / 10,000)
  costForThisPool = costPerPpm × (FC raise ppm)
  0.00834 = lb available chlorine per 1 ppm per 10,000 gal

Step C — the side-effect each product hides (per 1 ppm FC)
  Trichlor  +0.6 ppm CYA      Cal-hypo  +0.8 ppm CH
  Dichlor   +0.9 ppm CYA (2 chlorines per ring, not 3)
  Liquid    none

Why the side-effect column matters: trichlor often wins on raw $/ppm, but it adds cyanuric acid every dose — and once CYA climbs there is no chemical to remove it, only a partial drain-and-refill. That recurring cost is the "hidden cost" a $/ppm rank alone never shows. We flag a row when a single dose adds more than 5 ppm CYA or 8 ppm CH — a soft UX nudge, not a chemistry limit.

The 0.00834 lb/ppm/10k constant is the pure-chemistry conversion (1 ppm = 1 mg/L over 37,854 L), cross-checked against CleanPoolMath's published 10.8 fl oz of 12.5% liquid per ppm dose factor. Salt / saltwater generators are not included: their per-ppm cost is an amortization estimate (cell wear + electricity), not a price, so adding them would blur the exact liquid-vs-tablet comparison. The two CYA ratios are molar properties of the molecules — cyanuric acid 129.07 g/mol over 2 or 3 chlorines at 70.906 g/mol as Cl₂ — so they hold across brands and across hydrated or anhydrous dichlor.

Cost per ppm is one half of the decision; the other half is what the product does to your week. Tablets trade a good unit price for a feeder to load and a CYA creep to watch, and the chlorine tablet calculator sizes that load against your volume and burn rate. Whichever product wins here, the dose itself is still worked out on the chlorine dose calculator, and what the winning product leaves you on a monthly per-pool basis lands in the chemical cost and margin calculator.

Sources: HomeownersHub (normalization to $/lb available chlorine, weight conversions); Aquatics International (CYA/CH side-effect ratios); CleanPoolMath (dose-factor cross-check). This is a comparative estimate, not a guaranteed price or a water-safety claim.