What is a Discount Calculator?
A discount calculator instantly tells you the sale price and dollar savings when a percentage is knocked off the original price. It is the fastest way to check whether the tag reading "40% off $120" actually beats the coupon in your email inbox.
The Formula
Sale Price = Original × (1 − Discount% / 100)
The savings amount by itself is simpler:
Savings = Original × Discount% / 100
Where Original is the ticket price before any markdown and Discount% is the advertised percentage off.
Worked Example: $80 jacket at 25% off
Take an $80 jacket at 25% off. Savings = 80 × 0.25 = $20. Sale price = 80 − 20 = $60. If you also have a 10% coupon that stacks on the sale price, the second 10% is calculated off $60, not $80, so it takes another $6 off for a final price of $54.
Worked Example: Stacked discounts (20% off + 10% coupon)
Here is where shoppers overpay. A store advertises "20% off, plus an extra 10% at checkout." That is not 30% off. Start with $100: 20% off leaves $80, then 10% off $80 leaves $72. The effective discount is 28%, not 30%. The general rule for stacking two discounts a and b is: total = 1 − (1 − a)(1 − b). Three-way stacks compound the same way.
When to Use This Calculator
- Retail sales: compare Black Friday markdowns across stores fast.
- Coupon math: figure out whether stacking a store coupon on a clearance tag beats the flat percentage banner.
- Credit card cash-back: convert a 2% cash-back offer into equivalent-discount terms.
- BOGO (buy-one-get-one) offers: BOGO free is a 50% per-item discount; BOGO 50% is only 25% per item.
- Tax-free weekend planning: add your local sales tax rate to compare a "no tax" sale with a plain percentage discount.
Mistakes to Avoid
- Assuming stacked discounts add up: they multiply. 20% + 10% is 28%, not 30% — as shown above.
- Ignoring taxes: a "10% off" that excludes tax and shipping can turn into 3–4% real savings after fees.
- Trusting inflated "MSRP": some retailers raise the list price right before a sale so the discount looks steeper. Check the historical price on CamelCamelCamel or Honey before celebrating.
Frequently Asked Questions
How do stacked discounts work?
They multiply, not add. For two discounts a and b, the effective discount is 1 − (1 − a)(1 − b). A 30% + 20% stack is only 44%, not 50%.
Does the discount apply before or after tax?
Almost always before. Retailers apply the percentage off to the pre-tax price, then compute sales tax on the discounted amount. That is why the tax on the receipt looks smaller than expected — a feature, not a bug.
What is the difference between a dollar discount and a percentage discount?
A dollar discount is a fixed amount off ($10 off) regardless of price. A percentage discount scales with the price. On cheap items, "$10 off" beats "10% off"; on expensive items, the percentage wins. Break-even is when Original × % = fixed $.
How do I calculate the original price from a sale price and % off?
Divide the sale price by (1 − Discount% / 100). Example: a sale price of $60 at 25% off implies an original price of 60 / 0.75 = $80.