Change the rules on unit prices when you have a coupon

Submitted by a LOZO expert
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As most savvy shoppers know, unit price is an important way of comparing the "real" cost of different package sizes. Generally speaking, the lower the unit price, the better the deal, and larger packages usually offer a better unit price. See below for an easy-to-use unit price calculator.

For example, a 20 ounce package that costs $2 is like paying 10 cents per ounce ($2 / 20) while a 10 ounce package for $1.50 is like paying 15 cents per ounce ($1.50 / 10). The 20 ounce package is the better deal. You'll have to lay out more cash initially, but you make it back by not having to buy the item as often.*

However, the rules get turned around when coupons come into play. Very often the smallest packages--which had the worst unit price to start with--end up with the BEST unit price after deducting a coupon! If you have multiple coupons, or don't need to buy as much of the item at one time, you'll save more by purchasing the smaller packages.

Unfortunately, stores don't give you the unit price after the coupon has been factored in, so you have to do it yourself. Here's an example:

Without a coupon:
  • Choice 1: 20 ounce box for $5.00 ($5.00 / 20 or 25.0 cents per ounce)
  • Choice 2: 10 ounce box for $2.65 ($2.65 / 10 or 26.5 cents per ounce)
  • --> Choice 1 would be cheaper (25.0 cents vs. 26.5 per ounce)
With a "50 cents off" coupon
  • Choice 1: 20 ounce box for $4.50 after the coupon ($4.50 / 20 or 22.5 cents per ounce)
  • Choice 2: 10 ounce box for $2.15 after the coupon ($2.15 / 10 or 21.5 cents per ounce)
  • --> Choice 2 is cheaper now (21.5 cents vs. 22.5 cents per ounce)
As you can see, this will be easy enough to do with a basic calculator (your phone might even have one), a piece of paper, in your head, or with LOZO's handy unit price calculator! You can include a coupon to see which is the better deal, or leave that blank to compare base cost of the items.

LOZO's Unit Price Coupon Comparison Calculator

Item 1:

Item 2:

Coupon Discount:

Compare Unit Prices After Coupon

If you hate doing the math, these quick tips will give you the lowest price more often than not:
  • First choice: use the coupon on the package that's on sale. If more than one size is on sale, use it on the smallest one.
  • Second choice: if the coupon is worth at least 50 cents off, then use it on the smallest package. Exception: if the unit price for the smallest package is double the larger size, or if the coupon is for less than 50 cents, then go with the larger size.
*Really savvy shoppers know that the main exception to this rule is when certain package sizes go on sale. Very often in those cases, it will be a better deal to buy the sale item--even if a larger package is available. Since supermarkets provide unit prices even for sale items, you can still compare right on the shelf to make the right decision.

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