Unit prices can help you save on groceries

When packaged food and household products are sold in more than one size, the largest often is the best deal, with a lower cost per ounce, pound, or other unit. But that's not always the case, which means buying the bigger package won't always save you money on groceries over the long run.

Sometimes, instead of giving you a per-unit discount for a larger item, stores impose a so-called quantity surcharge for certain products, such as some brands of canned tuna, ketchup and laundry detergent. One study found that, in some supermarkets, as much as 25 percent of brand-name products are a poorer value in the larger size.

We found several examples during a recent visit to a New York Target store. For instance, a 40-ounce jar of Market Pantry peanut butter had a unit price $2.26 per pound, 9 cents per pound more than the 18-ounce size. A 150-fluid-ounce jug of Up&Up laundry detergent had a unit price of $2.86 per quart, about 5 cents more per quart than the 100-fluid-ounce jug. And the $4.12 per pound unit price for a 12-ounce can of StarKist tuna was a whopping 54 cents per pound more expensive than the 5-ounce one.

Watch our video on other unit price gotchas to be on guard against.

What to do

If you want to save money on groceries, don’t automatically buy the largest size. If the store has unit price labels, a requirement in some states, use those to find out which size package is the best deal based on the price per ounce, pound, or other unit. (But you may want to verify them. During our Target trip, the unit price for a 38-ounce bottle of Heinz ketchup was displayed as $1.14 per pound when it was actually was $1.20 per pound, making it virtually identical to the unit price of 64-ounce bottle.)

If a store doesn’t display unit prices (or doesn’t recalculate them when items are on sale), you’ll have to do some cogitating to come up with them yourself. Or you could use the calculator app built into your cell phone.

—Anthony Giorgianni

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