Discount Calculator: Calculate Sale Price and Savings

A discount calculation has three elements: the original price, the discount percentage, and the final sale price. The formula for the savings amount is: original price × (discount percentage ÷ 100). The sale price is then: original price − savings. For a $120 item at 25% off: savings = $120 × 0.25 = $30. Sale price = $120 − $30 = $90.

You can also calculate the sale price directly in one step: multiply the original price by (1 − the discount as a decimal). For a 25% discount: $120 × (1 − 0.25) = $120 × 0.75 = $90. This single-step method is faster when you only need the final price and do not need to know the savings amount separately.

If you know the sale price and the discount percentage but want the original price, reverse the calculation. Original price = sale price ÷ (1 − discount as a decimal). For a $90 sale price at 25% off: $90 ÷ (1 − 0.25) = $90 ÷ 0.75 = $120.

This reverse calculation is useful when retailers display only the sale price but you want to evaluate whether the original price was reasonable before the discount. It is also relevant for calculating what a price was before tax was added, or before a percentage markup was applied.

Stacked discounts — where a second discount applies to an already-discounted price — do not add together linearly. A 20% discount followed by an additional 10% discount does not equal a 30% total discount. The second discount applies to the already-reduced price.

The correct calculation for stacked discounts: apply the first discount, then apply the second to the resulting price. For a $100 item with 20% off then 10% off: $100 × 0.80 = $80 after first discount. $80 × 0.90 = $72 after second discount. Total effective discount: 28%, not 30%.

Percentage discounts can be misleading when comparing across different base prices. A 30% discount on a $50 item saves $15. A 10% discount on a $200 item saves $20. The larger percentage discount produces less absolute savings in this case. Always evaluate both the percentage and the absolute amount saved when comparing deals.

Retailers sometimes use higher percentage discounts on lower-priced items to create the impression of a better deal than a smaller percentage on a higher-priced item. Converting to absolute savings makes the comparison straightforward.

If a sale price still has tax added at checkout, calculate the discount first, then add tax. For a $120 item at 25% off with 8% tax: sale price after discount = $90. Tax = $90 × 0.08 = $7.20. Final price = $90 + $7.20 = $97.20.

Some jurisdictions calculate tax on the original price before discount, which increases the tax amount. Knowing the local tax calculation method affects whether the discount or the tax is applied first in your calculation. When in doubt, the receipt total is the authoritative number.

Use these benchmark pairs for fast sanity checks.