How discounts combine
A percentage discount multiplies the price by what is left after the discount: 25% off leaves 75%. When a store adds "an extra 10% off sale prices", that second percentage multiplies the already-reduced price, so stacked percentages never simply add up. A dollar-off discount is subtracted. Tax, if any, is applied last to the price you actually pay.
The formulas
Percent off: sale = price × (1 − d₁) × (1 − d₂) Dollar off: sale = (price − dollars) × (1 − d₂) Savings = price − sale; combined % = savings / price Total = sale × (1 + tax rate)
Worked example
A $120 jacket, 25% off, with an extra 10% coupon and 8% tax: 120 × 0.75 = $90, then 90 × 0.90 = $81.00.
You save $39.00, a combined discount of 39 / 120 = 32.5%. Tax is 81 × 0.08 = $6.48, for a total of $87.48.
Notes
- A dollar-off amount larger than the price gives a sale price of $0.
- The extra coupon is applied after the main discount, which is how most "extra % off" promotions are written. Check the store's terms.
- Amounts are rounded to the cent.
Frequently asked questions
Is 25% off plus an extra 10% off the same as 35% off?
No. The extra 10% applies to the already-reduced price, so the combined discount is 1 − (0.75 × 0.90) = 32.5%, not 35%. On a $120 item that is $81.00 instead of $78.00.
Does the order of stacked discounts matter?
For two percentage discounts, no — multiplication gives the same result either way. It does matter when one discount is a fixed dollar amount: on a $100 item, 20% off then $10 off leaves $70, while $10 off then 20% off leaves $72. Taking the percentage first is better for you; the store's terms decide which order applies.
Is sales tax charged on the original or the discounted price?
For a store discount or coupon, tax is normally charged on the discounted price, which is what the calculator does. Manufacturer coupons reimbursed to the store are taxed on the pre-coupon price in many states.
How do I find the original price from a sale price?
Divide the sale price by (1 − discount). An item on sale for $60 at 25% off was originally 60 / 0.75 = $80.
CalcNest results are estimates based on the inputs and assumptions above, not financial, tax or lending advice. A lender's official Loan Estimate or your account statement is the final word.