How it is calculated
Final price = price × (1 − d₁) × (1 − d₂) Real discount = 1 − (1 − d₁)(1 − d₂) Discount % = (old − new) ÷ old × 100Stacked discounts do not add up: 50% then 20% is a real 60% discount, not 70%.
Worked example
Shoes at 800 with 30% off and an extra 10% at checkout: 800 × 0.7 × 0.9 = 504, a real 37% discount.
Frequently asked questions
Is 50% + 50% free?
No — it is a real 75% discount, because the second applies to the already reduced price.
How do I get the % from two prices?
Choose “I know both prices” and enter the old and new price.
Before or after tax?
Consumer discounts usually apply to the tax-inclusive price; mathematically the percentage is the same.