Trust & methodology
Calculation Methodology
How ShopWithShery normalizes prices, handles discounts and separates observed inputs from assumptions.
Calculation rules
ShopWithShery keeps stable shopping mathematics separate from retailer-specific facts. Unit price divides effective price by usable quantity. Sequential percentage discounts multiply rather than add. Delivered-cost tools separate merchandise, shipping, fees and tax assumptions. Cashback and store credit are displayed separately from money paid at checkout.
What we do not infer
We do not guess whether a retailer will honor a coupon, whether tax applies to a particular fee, whether a product will last as long as expected, or whether a warranty claim will be approved. Those are retailer, jurisdiction and usage facts that the calculator cannot observe.