Salt Cell Sizing Calculator

Picking a salt cell is a sizing job, not a chemistry job. The industry rule of thumb is to fit a generator rated for 1.5×–2.0× the pool's gallons — oversizing on purpose so the cell runs at a relaxed 50–70% output instead of flat out. A right-sized cell lasts about 5–7 years; an undersized one running near 100% burns out in 2–3. We start at the 2.0× default and only slide toward the 1.5× floor when low-demand factors stack (shade, cool weather, light use).

oversizeFactor      = clamp(2.0 + min(0, demandScore), 1.5, 2.0)
recommendedRatedGal = poolGallons × oversizeFactor
recommendedClass    = smallest product tier ≥ recommendedRatedGal
                      [15k · 20k · 25k · 40k · 60k gal]
high demand (≥3 of 4 factors maxed) → one tier up

baselineOutput  = poolGallons / 10,000           (lb/day at 100%)
expectedRun %   = baselineOutput / (class / 10,000)  ≈ poolGallons / class

dimensions mode: poolGallons = pool-volume engine (shape × avg depth × 7.48 gal/ft³)
                 avgDepth = (shallow + deep) / 2 (deep blank ⇒ shallow)

Why two levers, not one. Low-demand conditions slide the oversize factor down toward 1.5×. High-demand conditions don't push the factor past 2.0× (the cited rule caps there) — instead they bump the recommendation up one real product tier, the way an installer steps from an IC40-class to an IC60-class cell. So a neutral 20,000-gal pool lands at the 40,000-gal class; the same pool in full sun with heavy use and water features steps up to the 60,000-gal class.

The run-% check. One pound of chlorine a day treats roughly 10,000 gallons, so a 20,000-gal pool needs about 2.0 lb/day, and a 40,000-gal-class cell (≈4.0 lb/day) covers that at about 50% output — the longevity sweet spot. The optional second panel turns a unit's published lb/day rating into the daily run hours and % setting, and flags a cell that can't keep up at the buffered target.

We snap to real product classes (15k / 20k / 25k / 40k / 60k gal), not an exact computed number, because installers buy SKUs — example references like Pentair IntelliChlor IC20/IC40/IC60 map to the 20k/40k/60k classes. This is a vendor-neutral planning aid; final selection should follow your chosen brand's sizing chart.

Sources: chlorine-generator.com — Salt chlorine generator sizing (the 1.5×–2.0× rule, bracket chart, demand factors, 50–70% longevity target); INYO Pools — How to Size a Salt Chlorine Generator (oversize-for- longevity, IC20/IC40/IC60 tiers); My Pool Calculator — Saltwater Generator Sizing (the 1 lb/day ≈ 10,000 gal baseline + 15–20% buffer).