Your figures
Result
How this calculator works
Enter the list price and the percentage off. The calculator reduces the price, shows exactly how much the customer saves, and then applies tax to the discounted amount — the order matters, because in most systems tax is charged on what is actually paid, not on the ticket price. An optional second discount field covers stacked promotions of the “extra 10% off sale prices” kind.
Stacked discounts are where intuition fails. Twenty percent off followed by another ten percent off is not thirty percent off: the second percentage acts on the already-reduced price, so the combined saving is 28%. The calculator spells this out in the results whenever you use the second field, because promotions planned on the additive assumption quietly give away less margin than the shop thinks — or, from the customer's side, deliver a smaller saving than the banner promises.
Good practice and limits
Plan promotions from the margin backwards. Take the post-discount price and run it through the margin calculator before the sale goes live, and include the costs that do not shrink with the price — card fees are usually charged on the amount paid, but picking, packing and delivery cost the same for a discounted order as a full-price one.