How to use this calculator
Each discount applies to the price remaining after the previous discount. The equivalent discount compares your total pre-tax saving with the original price. Currency changes only the display; it does not convert money.
The formula
Sale price = original × (1 − first discount ÷ 100) × (1 − second discount ÷ 100). Tax = sale price × tax rate ÷ 100. Final price = sale price + tax.
A worked example
A $100 item with 20% off costs $80. An extra 10% off that $80 makes it $72, a combined discount of 28%. At a user-entered 10% tax rate, tax is $7.20 and the final price is $79.20.
What to keep in mind
- Prices must be zero or positive; each discount and the tax rate must be between 0% and 100%.
- For a zero original price, all amounts are zero and the equivalent discount is not applicable.
- This is arithmetic using the rate you provide, not a determination of local tax law. Shipping, fixed-value coupons, and item-level tax rounding are excluded.
Formula v1.0.0 · Updated November 6, 2026 · Results: 2 decimal places for money, rounded half up. Very small nonzero values use scientific notation.