Percent Off Calculator — Stacked Discounts & Sales Tax
Calculate the true final price after stacked discounts and local sales tax. See why "20% off plus an extra 10%" is NOT 30% off, and get the real effective discount percentage.
Percent Off Calculator
Results update instantly as you type
Enter Values
Total Amount Saved
$38.40
Effective Total Discount
32.00%
"Stacking Gap" — looks like 35% off but you actually got
32.00% (3.00 percentage points less)
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You Save
$38.40
32.0% effective discount
Original
$120.00
Discounted
$88.33
The Formula
Stacked discounts multiply, they do not add. A 20% discount followed by a 10% discount does not equal 30% off — the second discount is applied to the already-reduced price, so the combined effective discount is always less than the sum of the two stated discounts. The formula also shows that sales tax is applied after all discounts, which means a larger discount actually reduces the amount of tax you pay as well.
Variable Definitions
Original Price
The pre-discount listed price of the item. This is the starting point before any discounts or tax are applied.
Sequential Discounts
Two discounts multiply, they do not add. A 20% discount followed by 10% off = 28% effective total discount ($100 → $72), not 30% ($70). The order of discounts does not matter since multiplication is commutative.
Sales Tax Rate
Local sales tax, applied to the final discounted subtotal. Always calculated after all discounts have been applied.
How to Use This Calculator
- 1
Enter the original price, the primary discount percentage, and any stacked second discount.
- 2
Add your local sales tax rate to see the true out-the-door price.
- 3
Notice the "Stacking Gap" — the difference between what discounts look like added together vs. what they actually multiply out to.
Common Applications
- Calculate the final price after multiple sequential discounts to avoid the common mistake of adding percentages together.
- Compare different coupon and promotion combinations to determine which stacking strategy saves you the most money.
- Include sales tax in your discount calculations to see the true out-the-door price for major retail purchases.
Sequential discounts always multiply — the second discount applies to the already-reduced price, creating a "stacking gap" that is smaller than the sum of discounts
Understanding the Concept
Sequential discounting is the most misunderstood pricing math in retail. If a sweater is $100 and a sign says "30% off, plus an extra 20% at the register," shoppers expect to pay $50 (50% off). The actual price is $100 × 0.70 × 0.80 = $56 — only 44% off. Retailers exploit this gap during Black Friday and clearance events because the headline number ("Up to 50% off!") is mathematically dishonest but legally fine. Always run the actual numbers before committing to a "stack." The "Stacking Gap" line in the results explicitly shows you how many percentage points you are losing to sequential math. This is particularly important for large purchases like furniture, electronics, or appliances where even a 2% gap can mean tens or hundreds of dollars.
Frequently Asked Questions
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