Advanced options
Stacked discounts multiply, they don't add: "25% off, then an extra 10% at checkout" is 32.5% off, not 35%, because the second discount bites a smaller number. Leave the second box at 0 for a plain single discount. And "was" prices are only meaningful if anyone ever paid them: check the price history on big-ticket sale items.
What The Discount Calculator Works Out
- You pay: the original price multiplied by (1 minus each discount) in turn. "25% off then an extra 10%" leaves 75% times 90%, which is 67.5% of the price, so GBP 80 becomes GBP 54.
- True total discount: 1 minus the final price over the original. Stacked discounts multiply rather than add: 25% and 10% is 32.5% off, not 35%, and "50% plus 50%" is 75% off, not free.
- Why not simply added: the second code bites the already-reduced price, so it is worth less than its headline percentage of the original.
- Third stacked discount (advanced): a further code, student discount or loyalty percentage, applied to the price after the first two.
- Money-off voucher (advanced): a fixed GBP amount, applied either after the percentages (the usual checkout order, worth its full face value) or before them (worth less, because the percentages then shrink it too). Retailers choose the order that favours them.
- Quantity and delivery (advanced): the basket total at checkout for several items plus any delivery charge. A GBP 4.99 delivery fee can wipe out a 10% code on a small order.
- Cashback (advanced): the percentage a cashback site or card returns on the goods price, and the effective cost once it arrives. Newsletter codes, cashback portals and card offers multiply like the percentages do.
- Rise needed to undo the discount (advanced): discount divided by (100 minus discount). A 20% cut needs a 25% rise to get back to the original price, which is why "back to full price" after a sale is steeper than the sale was generous.