The simple version

A shelf tag usually has a big price and a small one. The big price is what you pay for the package in your hand.

The small one is the price per ounce, per pound, or per item. It is the only number on the tag that tells you which size is actually cheaper.

The numbers

• The model regulation behind unit pricing has never included a mandatory provision, so showing a unit price is not required by federal law (National Institute of Standards and Technology, uniform unit pricing)
• Nineteen states and two territories have implemented unit pricing laws or regulations, and eleven of those jurisdictions have mandatory provisions (National Institute of Standards and Technology, same page)
• Citing a Bureau of Labor Statistics analysis in 2023, covering January 2019 to October 2023, the agency reports that approximately 30% of consumer goods were downsized and likely affected by shrinkflation over that period (National Institute of Standards and Technology, same page)

Why the big price cannot compare sizes

A package price bundles two things together: how much you get and what it costs. Two packages of different sizes can only be compared once those are pulled apart.

The unit price does that division for you. Price divided by quantity, shown in the same unit for every size on the shelf.

Larger packages are often cheaper per unit. Not always, and the only way to know on a given shelf is to read the small number.

When the package shrinks and the price does not

Sometimes a product keeps its price and quietly loses contents. The agency that maintains the model unit pricing rules connects unit pricing directly to this, and cites a federal statistics analysis putting it at roughly 30% of consumer goods over a four-year period ending in 2023.

The package price does not change, so nothing on the tag looks different. The unit price does change, because the same money now buys less.

That makes the small number the only one on the tag that shows the price went up.

The Real Cost lens on two tags

Here is the arithmetic with prices and sizes we chose.

• 16 ounces for $4.00 is $0.25 an ounce.
• 12 ounces for $3.29 is about $0.274 an ounce, roughly 10% more per ounce for the smaller package.
• If the 16 ounce package drops to 14 ounces and stays at $4.00, the price becomes about $0.286 an ounce.
• That is about 14% more per ounce, and the big number on the tag never moved.

Those figures are ours and describe no real product. The method works on any shelf: compare the small numbers, and only compare them when they are in the same unit.

What this means

Unit pricing is one of the few places where a store does the comparison arithmetic for you, when it chooses to or when its state requires it. Since the federal model rule has never made it mandatory, whether you get that help depends on where you shop.

One practical catch is that tags do not always use the same unit for every size of the same product. When one tag shows price per ounce and another shows price per pound, the comparison has to be converted first.

What this is NOT

This article does not recommend buying larger or smaller packages, and it names no store, brand, or product. Unit pricing is not required by federal law, and where it is required the rules come from individual states and territories and vary, so nothing here describes any particular jurisdiction's requirements beyond the counts the federal agency publishes. The downsizing figure is that agency's citation of a Bureau of Labor Statistics analysis in 2023 covering January 2019 to October 2023, so it describes that period and not today. The prices and package sizes in the Real Cost section are illustrations we chose and describe no real product. A lower unit price is not always the better purchase for a household, because it does not account for storage, spoilage, or whether the extra quantity gets used.

Sources

• National Institute of Standards and Technology, uniform unit pricing: https://www.nist.gov/programs-projects/uniform-unit-pricing-tools-consumers-fight-shrinkflation