Discount Calculator

A discount calculator handles the three questions that come up around a sale price: what's the final price after a percentage discount, what percentage discount does a sale price actually represent, and what happens when two or more coupons or markdowns are applied to the same item one after another. Enter the numbers you have and the tool calculates the rest, which removes the guesswork from a checkout math that's surprisingly easy to get wrong under pressure.

This is useful for shoppers comparing sale prices before checkout, retailers setting markdown pricing, and anyone trying to figure out whether a coupon stack is actually as good a deal as it sounds. The math behind a single discount is simple, but stacked discounts in particular behave in a way that isn't intuitive — most people assume percentages add together, and that assumption is wrong.

Doing this by hand isn't hard for a single discount, but it gets error-prone fast once a second coupon, a rounding step, or a reverse calculation (working backward from a sale price to the original) enters the picture. A calculator applies the correct formula for whichever direction you're solving, so the final number matches what the register will actually charge.

To find the price after a percentage discount, convert the discount percentage to a decimal and subtract it from 1, then multiply by the original price. The formula is: sale price = original price × (1 − discount ÷ 100). The amount saved is simply the original price minus the sale price, or equivalently, original price × (discount ÷ 100).

For example, a $100 item with a 20% discount: sale price = 100 × (1 − 0.20), or 100 × 0.80, which equals $80. The amount saved is $20, matching 20% of the original $100. The same formula works regardless of the item's price — a $250 item at 20% off follows the identical calculation, just with different numbers.

• Formula: sale price = original price × (1 − discount ÷ 100)
• Amount saved = original price × (discount ÷ 100)
• Example: $100 at 20% off → $100 × 0.80 = $80 sale price, $20 saved

Sometimes you already know the original price and the final sale price and want to know what percentage discount that represents — useful for comparing two different sales that are advertised with dollar amounts instead of percentages. The formula is: discount % = ((original price − sale price) ÷ original price) × 100.

For example, an item originally priced at $100 that's now selling for $80: ((100 − 80) ÷ 100) × 100 equals 20%. This works in reverse for any pair of prices — a $250 item now selling for $200 is also a 20% discount, since ((250 − 200) ÷ 250) × 100 equals 20% as well, even though the dollar amount saved is different.

• Formula: discount % = ((original price − sale price) ÷ original price) × 100
• Example: $100 original, $80 sale price → 20% discount

When two discounts apply to the same purchase, such as a storewide sale plus a coupon code, it's tempting to just add the two percentages together. That's incorrect, because the second discount applies to the already-reduced price from the first discount, not to the original price — the math has to be done as two sequential steps, not one combined percentage.

For example, a $100 item with 20% off followed by an additional 10% off: the first discount brings the price to $80 (100 × 0.80). The second 10% discount then applies to that $80, not the original $100, bringing the price to $72 (80 × 0.90). The combined discount is 28%, not the 30% you'd get by simply adding the two percentages together.

• Correct method: apply each discount to the running price, one after another
• Example: $100 → 20% off → $80 → additional 10% off → $72 (a 28% total discount, not 30%)
• Shortcut: multiply the surviving percentages together — 0.80 × 0.90 = 0.72, or 72% of the original price

If you know the sale price and the discount percentage that was applied but not the original price, you can work backward using: original price = sale price ÷ (1 − discount ÷ 100). This is useful for confirming an advertised discount actually matches the difference between the two prices shown, or for figuring out what an item cost before a markdown.

For example, if an item is on sale for $72 after a 28% discount, the original price is 72 ÷ (1 − 0.28), or 72 ÷ 0.72, which equals $100. This reverse calculation is also the right way to double-check a stacked-discount result — plugging the final price and the combined percentage back into this formula should return the original price you started with.

• Formula: original price = sale price ÷ (1 − discount ÷ 100)
• Example: $72 sale price after a 28% discount → $72 ÷ 0.72 = $100 original price

These terms describe the same underlying math — a reduction from an original price — but they're used in slightly different contexts. A discount is the general term for any price reduction, whether it's automatic at checkout or requires an action to claim. A markdown specifically refers to a retailer permanently lowering the listed price of an item, often for clearance or end-of-season inventory.

A coupon is a specific mechanism for claiming a discount, usually requiring a code, a physical clipping, or a membership, and coupons are the type of discount most likely to be stacked with a separate storewide sale. Regardless of the label, the calculation is identical once you know the percentage or dollar amount being taken off the current price — the terminology just describes how the reduction is being offered, not how it's calculated.