A common shopping mistake is assuming two discounts add together — that a 20% off sale plus an extra 20% off coupon equals 40% off. It doesn't. Each discount applies to whatever price is left after the previous one, so two 20% discounts stacked actually give you 36% off the original price, not 40%.
This calculator's "Find sale price" tab handles a single discount correctly; for stacked discounts, run the sale price through the calculator twice, using the result of the first as the input to the second.
No. Each discount is applied to the already-discounted price, not the original price, so stacked percentage discounts are always less than their sum would suggest. See the example above.
Use the "Find discount %" tab — enter the original and sale price, and it calculates the percentage automatically. The formula is (original − sale) ÷ original × 100.
Discounts are almost always applied to the pre-tax price, with sales tax then calculated on the reduced amount. If a retailer applies tax before the discount, that's unusual and typically worth double-checking at checkout.
"20% off" means you pay 80% of the listed price. "Extra 20% off" (common with clearance stacking) applies another 20% reduction to the already-discounted price — which is smaller in dollar terms than 20% of the original price, as shown in the stacking example above.