Discount formulas
Savings = original × (discount % ÷ 100). Final price = original − savings. Example: $80 at 25% off → savings $20, final $60. Equivalently, final = original × (1 − discount%/100).
Stacked discounts
Two sequential discounts are not additive. 20% then 10% off $100 is $80, then $72 — not 30% off. Apply each cut to the current price.
Sales tax
In most places tax applies to the discounted price. Calculate the sale price first, then tax. For percent basics see how to calculate a percentage.
Quick tool
Use the CalcNest discount calculator with common presets (10%, 20%, 50%) and copy the final price.