How the calculator applies discounts
The calculator takes the list price, applies the sale percentage, then the extra coupon percentage to the already-reduced price, then subtracts any fixed amount off. The per-item price is rounded to the cent, multiplied by the quantity, and tax is added to the item subtotal (and to shipping if you tick the box). This matches how most checkouts work, but a few retailers apply fixed-amount coupons first; if the total on the store’s own page differs by a few cents or dollars, that ordering is the usual reason.
Why 20% plus 10% is not 30%
Percentages stack multiplicatively. A $100 item at 20% off costs $80; a further 10% off $80 takes off $8, not $10, leaving $72 — a real discount of 28%. The calculator shows both the headline sum and the true figure so you can see how marketing arithmetic differs from checkout arithmetic. Our guide to discount math works through more examples.
Check the sale against a usual price
If you type the usual price you have seen for the item (from your own notes, a screenshot or a price-history site), the tool tells you whether the final price is above or below it. A “50% off” label means little if the list price was inflated. Read how to tell if a Black Friday deal is real for a short checklist.
Comparing two offers
Fill in Offer B to compare two stores or bundles. The comparison uses the all-in total (items + tax + shipping), so a cheaper sticker price with $12 shipping can lose to a slightly dearer one with free delivery. Use the unit-price box to compare different pack sizes fairly.
Limits
The tool does not know about member-only pricing, loyalty points, cashback, trade-in credits, rebates, gift-with-purchase or price-match policies. It also cannot know whether a store will honour a code at checkout. When you are about to pay, the number on the store’s own final page is the one that counts — use this tool beforehand to decide whether the deal is worth pursuing.