Sale Math That Saves Real Money

A 40 percent off sale followed by an additional 20 percent off is not 60 percent off. It is 52 percent off. Stacked discounts multiply they do not add. This basic math error costs consumers and confuses retail employees daily. Stacked discounts "40% off plus an additional 20% off" means: Original: $100 After 40% off: $100 * 0.60 = $60 After additional 20% off: $60 * 0.80 = $48 Total discount: $52 off = 52% off NOT 60% off The formula for stacked discounts: function stackedDiscount ( price , ... discounts ) { let final = price ; for ( const d of discounts ) { final *= ( 1 - d / 100 ); } return { finalPrice : final , totalSaved : price - final , effectiveDiscount : (( price - final ) / price * 100 ) }; } stackedDiscount ( 100 , 40 , 20 ); // { finalPrice: 48, totalSaved: 52, effectiveDiscount: 52 } The "percentage off" vs. "dollars off" decision Retailers choose between "30% off" and "$15 off" strategically. Research shows consumers prefer whichever sounds bigger: Under $100: percentage