Percent Off Calculator
Calculate the savings and final price for a percentage discount. Add quantity and sales tax, or work backward from a known sale price to the original price.
How to calculate a percentage discount
Percent-off and reverse-discount formulas
A discount rate is converted from a percentage to a decimal before it is applied. The reverse formula divides the known sale price by the fraction that remained after the discount.
Sale price = Original price × (1 − Discount ÷ 100)
Original price from sale price = Sale price ÷ (1 − Discount ÷ 100)
Final total = Sale price × Quantity × (1 + Tax ÷ 100)
Currency selection changes the display symbol and label only; it does not perform foreign-exchange conversion. Seller rounding and local sales-tax rules can produce small differences at checkout.
Quick percentage-off examples
Examples exclude sales tax and use one item.
| Original price | Discount | Savings | Sale price |
|---|---|---|---|
| $100.00 | 10% | $10.00 | $90.00 |
| $100.00 | 25% | $25.00 | $75.00 |
| $100.00 | 40% | $40.00 | $60.00 |
| $80.00 | 15% | $12.00 | $68.00 |
Methodology, assumptions and sources
The calculator uses standard retail discount equations. Values remain at JavaScript number precision during the calculation and are rounded to two decimal places only for currency display.
Tax is applied to the discounted subtotal. This is a transparent planning convention, not a determination of which items, fees, or discounts are taxable in a particular jurisdiction.
Sources:
- OpenStax — Discounts, Markups, and Sales Tax — discount, sale-price, and sales-tax equations.
Last reviewed: August 2026. OpenStax does not endorse Efficienco.