Discounts: how to read a sale without getting fooled
Real sales are rarely a clean "50% off a round number". The price is $849.99, the sticker says "33% off plus an extra 5% at the register", and the register is where the math actually happens. This calculator takes any price and any percentage and shows you both the amount saved and the final price — and the notes below cover the traps (double discounts, tax timing, BOGO deals) that make advertised savings smaller than they sound.
The two-step math
- Find the discount amount: (price × percentage) ÷ 100. For a $50 item at 20%: (50 × 20) ÷ 100 = $10.
- Find the final price: price − discount. $50 − $10 = $40.
The shortcut: a 20% discount means you pay 80% of the price, so just multiply by 0.80. A 25% discount means paying 75% (multiply by 0.75), and so on. The calculator above uses the two-step method so it also shows the amount you're saving, not just the final price.
The double-discount trap
"20% off, plus an extra 10% off" is not 30% off. The second discount applies to the already-discounted price. Take $100: 20% off makes it $80, then 10% off that $80 is another $8 — final price $72, which is a 28% total discount. The two discounts are multiplied together, not added. This is why "stacked" offers always sound better than they are.
Quick reference on a $100 item
| Advertised Discount | You Save | You Pay |
|---|---|---|
| 10% OFF | $10.00 | $90.00 |
| 15% OFF | $15.00 | $85.00 |
| 20% OFF | $20.00 | $80.00 |
| 25% OFF | $25.00 | $75.00 |
| 33% OFF | $33.00 | $67.00 |
| 50% OFF | $50.00 | $50.00 |
| 75% OFF | $75.00 | $25.00 |
Tax comes after the discount
In almost every jurisdiction, sales tax is applied to the discounted price, not the original sticker price. So for a $100 item at 20% off in an 8% sales-tax area: the discounted price is $80, and the tax is $6.40, giving a total of $86.40. Calculate the discount first, then add tax — the calculator handles the first step, and you apply your local rate to the result.
Comparing multi-buy offers
Not every sale is a percentage. Here's what the common alternatives actually work out to on a $10 item:
- Buy one, get one 50% off: you pay $15 for two items — $7.50 each, a 25% discount on the pair.
- Buy 3, get 1 free (3-for-2): you pay $30 for four — $7.50 each, also 25% off.
- Buy 2, get 1 free: you pay $20 for three — $6.67 each, about 33% off.
Enter the per-item price and the actual amount you'd pay into the calculator to see the effective discount before you commit.
Discount questions that keep coming up
Are taxes included in the discount?
Almost always no — tax applies to the final discounted price. Discount first, then tax, or the discount effectively gets diluted.
How do I stack two coupons?
Apply them in sequence, multiplying the remaining fractions. 10% off then 20% off means paying 0.90 × 0.80 = 0.72 — a 28% total discount, not 30%.
Is "50% off everything" ever really 50%?
Usually yes for the marked items, but check for "exclusions" and whether the store raised the "original" price first. Comparing the sale price against what the item normally sells for elsewhere is the real test.
Can a business use this for pricing decisions?
Yes — enter wholesale cost and a target discount to see what margin remains. For example, an item costing $40 sold at $60 with a "20% off" promotion still clears $48, keeping an 8% margin on cost.