Discount Calculator
Final price after one or two discounts, and what you save.
How it works
Stacked discounts multiply rather than add. 30% off then a further 20% off is not 50% off — it is 44%, because the second discount applies to the already-reduced price.
The effective discount output does that arithmetic for you, which is usually enough to tell whether a "extra 20% off sale prices" offer is as good as it sounds.