The dose is the transparent industry identity. Each pound of pure available chlorine raises free chlorine (FC) by a fixed amount per 10,000 gallons, because one US gallon of water weighs about 8.3454 lb. We compute the pure-chlorine mass for your FC raise, then divide by the product's available-chlorine percent to get the amount you actually scoop or pour, then convert to your chosen unit.

ΔFC        = max(0, target FC − current FC)        (ppm)
pure_lb    = volume_gal × ΔFC × 0.0000083454       (lb pure chlorine)
product_lb = pure_lb ÷ (strength% ÷ 100)

liquid / bleach:  fl oz = product_lb ÷ 9.7 × 128   (cups ÷8, qt ÷32, gal ÷128)
cal-hypo / dichlor: oz = product_lb × 16           (show lb at ≥ 1 lb)
trichlor:         tabs = ceil(product_lb × 16 ÷ tab_oz)

side effects (added per ΔFC ppm):
  dichlor / trichlor → CYA  ≈ 9 × ΔFC ppm
  cal-hypo           → CH   ≈ 4 to 7 × ΔFC ppm  (a range — sources disagree)
  liquid / bleach    → pH   ≈ 0.2 × ΔFC units
suggested target FC ≈ 0.075 × current CYA

The 0.0000083454 constant is 8.3454 lb/gal ÷ 1,000,000; it matches Calculator Academy's published oz = (V × ΔFC) / 7500 within rounding. The liquid conversion folds a sodium-hypochlorite solution density of about 9.7 lb/gal into one factor rather than asking you for density. Calcium hardness is shown as a range (4–7 × ΔFC) because the published ratios disagree — we do not invent single-decimal precision. Doses are pourable estimates, not lab accuracy: sunlight, bather load, and contaminants consume chlorine, so your measured result will differ.

Sources: Calculator Academy — Pool Chlorine Calculator; Clean Pool Math — Pool Chlorine Calculator; Pool & Spa News — ppm unit of measure; My Pool Calculator — chlorine dose; The Pool Nerd — FC = 7.5% of CYA.