Discount Calculator
A discount calculator finds the final price of a product after applying one or more percentage discounts, showing exactly how much money you save. It handles the common shopping scenario of stacked discounts — for example, a 30% sale price with an extra 10% coupon at checkout — which does not equal 40% off, a mistake that costs shoppers real money. The calculator breaks down each reduction step by step, so you always know the true price before reaching the register.
Stacked (chained) discounts are applied sequentially: each new percentage is taken from the already-reduced price, not the original. That is why a 30% + 10% combination yields an effective discount of 37%, not 40%. Beyond shopping, the same math is used by retailers setting promotional pricing, freelancers offering bundled rebates, and B2B buyers negotiating tiered trade discounts. Seeing the effective discount percentage and total savings at a glance makes comparing offers straightforward and prevents misleading promotions from inflating perceived value.
How it works
A single discount is calculated as Final Price = Original Price × (1 − d), where d is the discount as a decimal; the savings equal Original Price × d. For stacked discounts, each rate multiplies the running price: Final Price = Original × (1 − d₁) × (1 − d₂) × … The effective total discount is 1 minus that product. Example: $100 with 30% then 10% off gives 100 × 0.70 × 0.90 = $63, an effective discount of 37% — not 40%, because the second discount applies to $70, not $100.
Use cases
- Checking the real final price when a store combines a sale with an extra coupon
- Comparing which of two promotions actually saves more money
- Setting promotional prices as a retailer and verifying the resulting margin
- Calculating tiered or chained trade discounts in B2B purchasing
Frequently asked questions
How do I calculate 20% off a price?
Multiply the original price by 0.20 to get the savings, or by 0.80 to get the final price directly. For a $150 item, 20% off means $30 in savings and a final price of $120. The general rule is Final Price = Original × (1 − discount rate).
Is 30% off plus 10% off the same as 40% off?
No. Stacked discounts are applied one after another, so the 10% is taken from the already-reduced price. On $100, 30% off gives $70, and 10% off that gives $63 — an effective 37% discount. A straight 40% discount would give $60, which is cheaper.
How do I calculate the discount percentage between two prices?
Subtract the final price from the original price, divide by the original price, and multiply by 100: (Original − Final) ÷ Original × 100. If an item dropped from $80 to $60, the discount is (80 − 60) ÷ 80 × 100 = 25%.
Does the order of stacked discounts change the final price?
No. Because each discount is a multiplication, the order does not matter: 30% then 10% gives × 0.70 × 0.90, and 10% then 30% gives × 0.90 × 0.70 — both equal × 0.63. The final price and effective discount are identical either way.
How do I add sales tax after a discount?
Apply the discount first, then compute tax on the reduced price, which is how most jurisdictions handle it. For a $100 item with 25% off and 8% tax: discounted price $75, tax $6, total $81. Some regions tax the pre-discount price for certain coupon types, so check your local rules if the amount matters.