Discount Calculator

The Discount Calculator figures out what you actually pay and what you actually save when a price is marked down. Every shopper and retailer runs this calculation constantly: a coat is marked 40% off from $180, what is the sale price? A coupon takes $15 off any purchase over $100, is it better than 15% off? The store is running an extra 25% off already-discounted items, what is the final price on a $200 item at 30% off plus 25% off? Reversal is also common: if something is now $72 after 40% off, what was the original price?

This calculator handles every discount pattern. Straightforward percent-off and dollar-off with instant sale price, savings, and effective percentage. Stacked discounts (also called compound discounts) applied sequentially in the correct order (first discount reduces price, second applies to the new reduced price). Tax can be added before or after discount depending on jurisdiction rules. Reverse calculations show the original price from any sale price. Multi-item totals handle BOGO (buy-one-get-one) and volume discounts correctly. Every result shows the formula so you understand how the numbers work, not just what they are.

Discount math looks trivial but has three pitfalls that come up constantly in commerce.

Simple percent discount: sale price = original × (1 - discount/100). A 40% discount on $180 gives $180 × 0.60 = $108. Savings = $180 - $108 = $72, or equivalently $180 × 0.40 = $72.

Stacked discounts are not additive. A 30% discount followed by a 25% discount is not 55% off. The first discount gives $100 × 0.70 = $70, then the second gives $70 × 0.75 = $52.50. The effective total discount is (100 - 52.50)/100 = 47.5%, not 55%. This confuses shoppers and sometimes retail staff. The correct formula for n stacked percentages is: final = original × (1 - p1/100) × (1 - p2/100) × ... × (1 - pn/100).

Fixed-amount discount: sale price = max(0, original - amount). The max ensures you do not go below zero if the coupon exceeds the price.

Tax handling varies. In the US, most states apply tax after discount (tax only applies to what you actually pay). Some jurisdictions, and some specific discount types (manufacturer coupons vs store coupons), apply tax to the pre-discount price. The calculator supports both modes so you can match your local rule.

Reverse calculation (original from sale price): original = sale_price / (1 - discount/100). $72 after 40% off: 72 / 0.60 = $120. People sometimes try to calculate this by adding 40% to $72, which gives the wrong answer: $72 × 1.40 = $100.80, not $120.

BOGO (buy one get one free): if you buy two items at $50 each and one is free, total is $50 for two, which is a 50% effective discount per item. BOGO half-off gives a 25% effective discount per item. The calculator handles these explicitly with a BOGO mode that shows per-item and total savings.

Multiple-item volume discounts (10% off when you buy 3+, for example) are computed on the full total, which is standard but worth confirming with the retailer — some apply per-item.

Compared to mental math at the register, this calculator gives instant accuracy for stacked discounts where mental math fails. For simple 20%-off math you can do it in your head; for the coupon-on-sale-with-tax-on-top scenarios, the calculator saves errors.

Compared to generic percentage calculators, this one is specifically built for shopping scenarios: stacked discounts applied correctly, BOGO handling, tax before/after options, reverse lookup for tags that only show sale price. The percentage calculator is a building block; this tool is the building.

Compared to retailer apps that do the math for you at checkout, this tool works before you commit to buying — you can check whether a deal is actually as good as the marketing claims, or compare across retailers without signing in to each one.