Work out sale prices, spot the real percentage off, or reverse-engineer the original price — pick what you're solving for below.
Quick answers to the questions people ask most about discounts.
Multiply the original price by the discount percentage (as a decimal) to find the amount saved, then subtract that from the original price. For example, 20% off $150 saves $30, so the sale price is $120.
Divide the sale price by (1 minus the discount as a decimal). For example, if you paid $120 after a 20% discount, the original price was $120 ÷ 0.80 = $150.
Subtract the sale price from the original price, divide that by the original price, then multiply by 100. For $150 down to $120, that's (30 ÷ 150) × 100 = 20%.
Stacked discounts apply one after another, not added together. Two 10% discounts on $100 give $100 × 0.90 × 0.90 = $81, a 19% total saving — not 20%, because the second discount applies to the already-reduced price.