Bulk vs regular packs: unit cost including unused quantities
Bulk vs regular packs: unit cost including unused quantities. Regular effective unit cost; Maximum unused percent at break-even.
Use the same quantity unit for both packs and weekly usage; no automatic conversion. For food, detergents, pet supplies and household consumables. Enter usable weeks after checking packaging and storage conditions. No food safety expiry is inferred; weeks start blank. Starting prices and usable percentages are editable examples. Positive differences mean bulk effective unit cost is higher. Unused value uses purchase unit cost. Maximum unused percent is the equal-cost boundary; below it bulk is cheaper per usable unit. No purchase recommendation.
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Method
Bulk expected usable quantity = min(Bulk quantity (same unit), Weekly usage (same unit) × Usable weeks (check packaging/storage)); Regular effective unit cost = Regular pack price ÷ (Regular quantity (same unit) × Regular usable percent (optional, default 100) ÷ 100); Bulk effective unit cost = Bulk pack price ÷ Bulk expected usable quantity; Required usable percent at break-even = Bulk pack price ÷ Regular effective unit cost ÷ Bulk quantity (same unit) × 100; Maximum unused percent at break-even = 100 − Required usable percent at break-even.