Unit pricing makes comparing products—from one brand to the next or between different sizes—more like comparing apples to apples, so it's easier to see which item really saves you the most money. Unfortunately, the unit pricing on the labels you see at the grocery store isn't always reliable.
To recap: unit pricing takes the price of the item (say, $1.59 for a 24-ounce jar of spaghetti sauce) and divides it by a standard unit of measurement (such as ounces) to provide a simple price comparison point ($1.59 divided by 24 ounces = $0.07 per ounce). You can then use that unit price to see if you're getting the best deal. Will the 45-ounce jar of sauce at $3.69 save or cost you money? Doing the math ($3.69 divided by 45 ounces = $0.08 per ounce), the answer is no; buy the smaller jar.
Usually you'll see the unit price on the shelf price label at grocery stores and big box retailers like Target and Wal-Mart. Despite their seeming helpfulness for smart shoppers, though, you can't always trust them.
Unit Pricing Isn't Regulated or Required in All States
According to the National Institute of Standards and Technology (NIST), only 19 states and 2 territories have unit pricing laws and regulations, and only 11 have mandatory unit pricing rules (i.e., how unit prices should be calculated and displayed). That means that 31 states don't have firm requirements for these pricing labels. The unit pricing you (may or may not) see on a label could vary greatly from one store to another or even between products within the same store, depending on where you live.
The states that have mandatory unit pricing provisions are: Connecticut, Maryland, Massachusetts, New Hampshire, New Jersey, New York, Oregon, Puerto Rico, Rhode Island, Vermont and the Virgin Islands. You can check the pricing laws and regulations for your state from this NIST page.
Missing Unit Prices
Stores in states that don't have mandatory unit pricing rules can still choose to add a unit price calculation on their price labels for the convenience of their customers—or choose to omit them altogether.
How-To Geek's Lowell Heddings, who tipped us off to this issue, noticed that the Target near him—he's in a state without mandatory unit pricing laws—started to take down the per unit pricing labels. Even more curious, the pricing for laundry detergent seemed off. Usually, larger sizes of a product are a better deal—buy the larger size or in bulk and pay less per unit. In his case, the larger size of the same laundry detergent brand and product cost more. There was no per unit price label to highlight that difference…but maybe that was the point.
Inconsistent Unit Pricing
Even if a store does display a unit price on the label, you have to be careful when relying on it. Some states have a requirement that the per unit measurement (e.g., ounces versus quarts) must be the same for each product within the category—but other states do not.
So you might see some flavors of tea priced by the quart on some labels or per 100 tea bags on others. And even if the unit measurement is the same—a dozen eggs, for example—the calculations of these unit prices can be very inconsistent, as the labels above from a Target in New York demonstrate. David S. Read, who took the photo, says:
Unit pricing is
supposed
to help people make informed decisions about the price difference between options. It is irritating enough when the unit price for a "value" or "saver" size is higher than the regular size. But at least the shopper who is paying attention can readily identify the deception.
More troublesome is looking at a group of products and finding that their unit prices don't use a consistent unit. For example, I've looked at cereals and had some brands give a unit price per ounce and others per pound. Worse, I've seen volume and weight measures used on similar products. Clearly such a store doesn't want me (the consumer) to have an easy path to understanding the relative prices of those items.
Items on sale also don't often include a per unit price on the label, which could also throw you off.
Unit Confusion
Some products are just trickier to compare with the unit price because they vary a lot by type. Paper towels, for example, often have a "per 100 sheets" unit pricing, but sheet sizes aren't the same for all brands, and select-a-size paper towels will have more (but smaller) sheets, giving them a lower cost per 100 sheets than full-sheet paper towels—even if the select-a-size ones are more expensive. A better way to calculate the value is to do it on total square feet per roll, Consumer Reports says.
Laundry detergent with different concentrations (e.g., 2x the washing formula) can also be confusing, when they're priced per fluid ounce. In these cases. Consumer Reports says to look at the number of loads per container listed on the bottle and use that as your unit for comparison.
Similar math needs to be done for toilet paper, with all its single-ply, double-ply, "mega roll" and other craziness.
Fuzzy Math, Swapped Products, and Other Stocking Errors
And then there are just the normal human errors that can lead us astray. You're looking to grab an item quickly off the shelf and check the per unit shelf pricing—but the shelf price is incorrect or the products are swapped, as the Walmart example from Cockeyed.com above shows.
Or the price per unit calculation is simply wrong, as in this comparison shopping example highlighted on Consumerist:
The single 10 oz. bottle of Alcon Opti-Free contact solution costs $8.99, while the twin pack, with 20 oz. total, costs $18.99–$1 more than two single bottles," he points out. If you break down the math, things get more confusing. The shelf tag measures the price per pint for some reason, and a pint is sixteen ounces.
Yet if you divide $18.99 by 20 for the per-ounce price and then multiply it by 16 again, you get $15.19 per pint.
States with pricing regulations have set guidelines for how much error is allowed on the price labels. In New York, for example, if at least 96% to 98% of items (depending on the store size) are accurately priced, the remaining 2 to 4% of pricing label errors are acceptable to the industry regulators. We shoppers might feel differently about that.
The Solution: Do the Math Yourself
The takeaway is that you can't really trust the unit pricing labels to always figure out which is really the better buy. If the store has the unit pricing on the label, it could help you comparison shop, but it could also lead you astray.
The solution is to calculate the per unit price yourself—yes, even if there's already unit pricing on the label. This is tedious and annoying, but it's the only way to compare prices for sure. We've mentioned two apps before that can help: Unit Price Compare for Android (free) and CompareMe Shopping Utility for iOS ($1.99). You might also consider keeping a price book so you know the typical sales prices (and per unit prices) for the groceries and household items you buy most.
Finally, remember that larger and bulk buys don't always offer the better value, and steer clear of grocery stores' other deceptive tricks.
Photo by lupuliuss (Shutterstock), Mike Mozart.