Discount Calculator: Stacked Savings and Sales Tax
Calculate two successive percentage discounts, effective savings and tax on the discounted price. See why 20% plus 10% off is a 28% discount.
Your inputs
Your result
Enter your values, then choose Calculate.
Estimate based on your inputs. Fees, taxes and market changes are included only where explicitly entered.
Calculation breakdown
Method, assumptions and worked example
Discounted price = original price × (1 − first discount ÷ 100) × (1 − second discount ÷ 100). Tax is then applied to that discounted price. Effective discount compares the final pre-tax price with the original price.
Worked example
Start with 100. After 20% off, the price is 80. A further 10% off saves 8, leaving 72. That is 28% off overall, not 30%. With 5% tax on 72, the final price is 75.60.
Use 0 for the second discount if there is only one offer. A 100% discount results in zero price and zero modeled tax. For a zero original price, savings are zero and the percentage display uses zero rather than dividing by zero.
Check whether the seller allows coupons to stack. This tool assumes both reductions are percentages and tax is charged after both; local coupon-tax treatment, shipping, minimum spends, fixed-value coupons and tax-inclusive pricing may differ.
Frequently asked questions
Can I add two discount percentages together?
No. Successive discounts apply to successively smaller prices. Multiply the retained price factors instead.
Is tax always calculated after coupons?
Not necessarily. The tool assumes tax applies to the discounted price; check your retailer and local tax treatment.
Sources and review
Formula and content reviewed on 9 October 2026. Examples are hypothetical. Tax years and model limits are stated above; this page does not receive live rates.