How the savings are worked out
Coupons come off one after another. A percent coupon multiplies the current price by one minus the percent; a dollar coupon subtracts its amount, down to zero.
Percent coupon: price × (1 − p ÷ 100) Dollar coupon: price − d
Dollar coupons stop at $0.
Example: when order matters
A $120.00 item with a 20% coupon and a $15.00 coupon.
- Percent first: $120.00 × 0.8 = $96.00, then − $15.00 = $81.00 (32.5% off)
- Dollars first: $120.00 − $15.00 = $105.00, then × 0.8 = $84.00 (30% off)
Example: buy 1 get 1 free
Three items at $25.00.
- One group of 2 means 1 free item; the third is full price
- You pay $50.00 instead of $75.00: 33.33% off
Questions
Does the order of coupons matter?
Sometimes. Two percent coupons give the same price in either order, and so do two dollar coupons, but a percent coupon with a dollar coupon does not (see the first example). The result tells you when it matters.
What if a dollar coupon is more than the price?
The price stops at $0.00 and never goes negative.
What does “effective % off” mean?
Total saved divided by the original price. Stacked percents do not add: 20% and 10% off save 28%, not 30%, because the second works on the lower price.
How are buy X get Y deals counted?
For identical items: in every group of X plus Y, Y are discounted. Buy 2 get 1 on five items discounts one, because only one full group of three fits. If the deal discounts the cheaper item, enter the average price.