How to calculate a percent off
A percent off tells you what fraction of the price is being removed. To get the sale price, convert the percent to a decimal, subtract it from one, and multiply by the price — so 30% off means you pay 70% of the original. The dollars saved are just the price times the percent as a decimal. Where it gets tricky is a second “extra % off” coupon, which comes off the already-reduced price, and sales tax, which is added on top of whatever you actually end up paying.
The percent-off formula
Sale price = Original × (1 − percent ÷ 100)
For example, 50% off a $100 item gives $100 × 0.50 = $50. Now add an “extra 20% off the sale price.” That extra coupon doesn’t make it 70% off — it comes off the $50, taking another $10, for a final price of $40. That’s a 60% effective discount, because the two percents multiply: 1 − (1 − 0.50)(1 − 0.20) = 1 − 0.40 = 0.60. Add sales tax to that $40 to see the real register total.
Worked example
Say a $80.00 sweater is marked 25% off, with no extra coupon and no sales tax. Here is the whole calculation from list price to sale price:
| Step | Amount |
|---|---|
| Original price | $80.00 |
| − 25% offthe dollars you save — 25% of $80.00 | $20.00 |
| = Sale priceyou pay 75% of the original; with no stacked coupon and no sales tax, the register total is also $60.00 | $60.00 |
Computed with this calculator's default settings — open the tool above and you'll see the same numbers, then add a stacked coupon or your local sales tax to match a real deal.
Percent off, stacked coupons and sales tax handled
- Sale price and savings together. Type a price and a percent off and see both what you’ll pay and how many dollars you save, with no mental math.
- Stacked coupons done right. Add a second “extra % off” and we multiply rather than add — and show the true combined discount next to the inflated number shoppers usually assume.
- The real out-the-door price. Sales tax is applied to the discounted price so you see exactly what you’ll hand over at the register.
- A clear breakdown. A line-by-line path from list price to final price shows where every dollar of savings comes from.
Frequently asked questions
How do I calculate a percent off a price?
Take the percent off, divide it by 100 to turn it into a decimal, and subtract that from 1, then multiply by the price: sale price = price × (1 − percent ÷ 100). For 30% off a $40 item, that’s $40 × (1 − 0.30) = $40 × 0.70 = $28. To find the dollars saved instead, multiply the price by the percent as a decimal: $40 × 0.30 = $12. This calculator returns both the sale price and the amount saved at once.
How much do I save with X% off?
The amount you save is simply the original price times the percent off as a decimal. With 25% off a $120 jacket, you save $120 × 0.25 = $30, leaving a sale price of $90. With 40% off, you’d save $48 and pay $72. The bigger the price tag, the more a given percent is worth in real dollars, which is why the same 20%-off sale matters far more on a $500 item than on a $20 one.
Do 50% off plus an extra 20% off add up to 70% off?
No — they multiply rather than add, so the real discount is 60%, not 70%. The extra 20% comes off the already-reduced price, not the original. Start at 50% of the price after the first cut, then take 20% off that, which leaves 80% of 50%, or 40% of the original — a 60% effective discount. In general two discounts of a% and b% combine to 1 − (1 − a)(1 − b), and the result is always smaller than simply adding the two percentages.
How do I work out the original price from a sale price and percent off?
Divide the sale price by one minus the percent off as a decimal: original = sale price ÷ (1 − percent ÷ 100). If something is on sale for $63 after 30% off, the original was $63 ÷ 0.70 = $90. This “reverse” step is handy for checking whether a marked-down price really reflects the advertised discount. Don’t just add the percent back on — adding 30% to $63 gives $81.90, which is wrong, because the percent was taken off the larger original number.
Is sales tax applied before or after the discount?
In almost every US jurisdiction, sales tax is charged on the final discounted price — you’re taxed on what you actually pay, not the original list price. So the order is: take the percent off first, then add sales tax to the reduced amount. A $100 item at 20% off becomes $80, and an 8% sales tax on that $80 adds $6.40 for a register total of $86.40. (Manufacturer rebates can be an exception in some states, where tax is figured before the rebate.)
Disclaimer: This calculator is for educational purposes only. Sales-tax rules and how discounts, coupons, and rebates are applied vary by retailer and location. It is not financial advice.