How the discount calculator works
A percentage discount multiplies the price by what is left after the discount. Stacked discounts apply one after the other, not added together, and sales tax is applied to the discounted price.
Final price = Sale price × (1 + tax rate)
Total discount = 1 − Sale price ÷ Price
That is why "25% off, then an extra 20% off" is a 40% total discount, not 45%: the second discount applies to the already reduced price. In most US states sales tax is charged on the price after store discounts; manufacturer coupons are sometimes taxed on the pre-coupon price.
Worked example
A $120 jacket is 25% off with 8% sales tax. The sale price is 120 × 0.75 = $90.00 and you pay 90 × 1.08 = $97.20 at the register, saving $30. Add an extra 20% off coupon and the sale price becomes 90 × 0.8 = $72.00, a 40% total discount, and you pay $77.76 with tax.
Frequently asked questions
How do I calculate a percentage discount?
Multiply the price by the discount rate to get the savings, then subtract it. Or multiply the price by (1 − rate): $80 × 0.85 = $68 for 15% off.
Do two discounts add together?
No. 30% off then 10% off equals 37% off, because 0.7 × 0.9 = 0.63.
Is sales tax charged before or after a discount?
Usually after store discounts. Rules for manufacturer coupons vary by state.
How do I find the original price from a sale price?
Divide the sale price by (1 − discount). A $68 item at 15% off was $80.
Updated October 2026. Results are estimates for education, not financial or medical advice. All math runs in your browser; nothing you type is sent anywhere.