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.
What makes this calculator different
- 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.