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.
Inflated "original" prices. Some retailers raise a price shortly before a sale, then advertise a large "% off" from that inflated number — meaning the "discount" may be smaller (or nonexistent) compared to the item's typical price over time. Price-tracking browser extensions or simply remembering what something cost last month are the practical defenses here.
"Up to X% off." This phrase technically only guarantees that at least one item in the sale has that discount — most items may be discounted far less. It's worth checking the actual price of the specific item you want rather than assuming the headline percentage applies broadly.
Bundled and tiered discounts. "Buy one, get one 50% off" isn't a 50% discount on the total — it's 50% off only the second item, making the effective discount on the full purchase 25%. Working this out with the calculator: two items at $40 each, second discounted 50% ($20), total paid $60 instead of $80 — a 25% effective discount, not 50%.
Major shopping events (Black Friday, end-of-season clearance, holiday sales) often combine a storewide percentage off with an additional coupon code or loyalty discount — exactly the stacking scenario covered above. Before assuming the discounts simply add together, run the math: a 30% off sale plus a 15% off coupon isn't 45% off, it's about 40.5% off (0.70 × 0.85 = 0.595, so you pay 59.5% of the original price, a 40.5% total discount).
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.
Yes, when buying exactly two of the same item — the discount only applies to the second item, so the total effective discount across both items works out to 25%, not 50%. This is a common source of confusion in retail promotions.
Compare the "original" price against what the item has actually sold for recently, not just the number on the tag — some retailers raise prices shortly before marking them "on sale." Price-history browser tools or simply remembering a recent price are practical ways to check whether a discount is real.