What a percent off calculator does
The percent off calculator turns a sticker price and a discount into the actual amount you'll pay — including the parts that get tricky in real shops: a second discount on top of the first, and sales tax applied after both. The result updates live, so you can compare two coupons in seconds without doing the maths in your head.
The simple percent off formula
For a single discount, multiply the original price by the discount as a decimal to get the amount saved, then subtract:
Sale price = Original × (1 − Discount ÷ 100)
For a stacked second discount, apply it to the already-discounted price. For sales tax, multiply the sale price by (1 + tax ÷ 100).
Stacked discounts: 30% + 20% ≠ 50%
This is the single trick that catches shoppers out. When a 20% off coupon is applied on top of a 30% sale, it's 20% off the already-reduced price — not a combined 50%. The math: 0.70 × 0.80 = 0.56, so you pay 56% of the original and save 44%. The calculator shows this explicitly in the step-by-step section so the "effective discount" is obvious.
Sales tax comes after
In the United States, sales tax is calculated on the price you actually pay — that is, on the post-discount total. So a $100 item with a $20 discount and 8.25% tax is taxed on $80 (not $100), giving a final price of $86.60. The calculator follows that convention. A few states tax some categories differently; if your receipt does something unusual, check your state's department of revenue rules.
Tips that help in real shops
- Always check the unit price. A "buy 3 for $10" stack can be worse than the per-item sale price next to it.
- Read coupon order. Some retailers require you to apply the larger discount first; others stack mathematically the same either way (multiplication is commutative). The math will be identical here regardless.
- Free shipping breakpoints. Sometimes a tiny add-on to reach the free-shipping threshold is cheaper than paying shipping on a smaller order.
- Final out-the-door price. The number that matters is what you actually swipe — that's what this calculator's "final price" box shows.
Use with other calculators
For other percentage questions — tips, grades, what-percent-of-what — use the percentage calculator. For US tax-rate questions, the federal income tax percentage calculator shows marginal vs effective rate.