Shrinkflation Calculator
The package before and after
Your result will appear here
Fill in the fields on the left and this updates as you type.
Know what this estimate is based on
- Jurisdiction
- General mathematical model
- Scope and limitations
- Educational estimate only. Confirm the assumptions, current rules, fees, and rounding that apply to your situation before making a decision.
- Source links checked
- Jul 30, 2026
Built and regression-tested by Smart Tools Lab. It has not been individually reviewed by a licensed financial, tax, or legal professional.
How to use
- 01
Find the old package's size and price, from a receipt, an old listing or your memory of the shelf tag.
- 02
Enter the new package's size and price, with both sizes in the same unit: ounces, grams, count or sheets.
- 03
Enter how many of these packages your household buys in a year.
- 04
Read the real rise in the price per unit, and how much of it sits on the sticker and how much is hidden in the smaller package.
- 05
Check the yearly figures and the side-by-side table, including what the new package would cost at the old price per unit.
Formula
Old price per unit = old price ÷ old size, and new price per unit = new price ÷ new size. Real price rise = new price per unit ÷ old price per unit − 1. Visible change = new price ÷ old price − 1. Size change = new size ÷ old size − 1. The hidden part, in percentage points, is the real rise minus the visible change. The new package at the old price per unit = new size × old price per unit. Extra a year for what you now get = packages a year × (new price − that fair price). Extra a year to get as much as before = packages a year × old size ÷ new size × new price − packages a year × old price.
Example
A cereal box shrinks from 18 ounces at $4.49 to 15.4 ounces at $4.79. The price per ounce goes from about $0.249 to $0.311, a real rise of 24.7%. The sticker rose only 6.7% and the box shrank 14.4%, so 18.0 points of the rise are hidden in the package. At the old price per ounce the new box would cost $3.84, so each one costs $0.95 more than it should. A household buying 24 boxes a year pays $114.96 instead of $107.76 while getting 369.6 ounces instead of 432.0. That is $22.77 a year more than the old price per ounce for the cereal it now gets, and getting as much as before would take 28.1 boxes and $26.61 more a year.
Definitions
- Shrinkflation
- A price increase made by reducing the amount in a package while keeping the price the same or raising it less than the size fell.
- Price per unit
- The price divided by the amount in the package, such as dollars per ounce. It is the only fair comparison between packages of different sizes.
- Visible price change
- The change in the price on the tag, ignoring any change in how much the package holds.
- Hidden price change
- The part of the real price-per-unit increase that comes from the smaller package rather than from the tag, measured here in percentage points.
- Net contents
- The amount of product in a package as stated on the label, by weight, volume or count, rather than the size of the box.
Good to know
Measuring a price rise when the package shrinks
A price tag answers one question: what this package costs today. It does not tell you what you are paying for the thing inside it. When manufacturers reduce the amount in a package, the tag can stay the same or rise a little while the real price climbs much faster. The only reliable way to see that is to compare the price per unit, per ounce, per sheet or per count, before and after the change. The arithmetic is simple. Divide each price by the amount in its package and compare the two results. This page's example is a box of cereal that went from 18 ounces at $4.49 to 15.4 ounces at $4.79. The old box cost about $0.249 an ounce and the new one $0.311. That is a real price rise of 24.7%, nearly four times the 6.7% rise on the tag. The same arithmetic answers a practical question: what the new package would cost if the price per ounce had not changed. Multiply the new size by the old price per ounce, and the 15.4-ounce box would sell for $3.84. Each box at $4.79 therefore costs $0.95 more than the old pricing would charge. Two details make the comparison trustworthy. First, use the same unit for both packages. A net weight in ounces and one in grams, or a count of rolls against a count of sheets, will produce a meaningless ratio. Second, use net contents from the label, not the dimensions of the box. A package can keep its outside size while holding less, which is often how a size change goes unnoticed. With those two checks, the price per unit tells you what really happened to the price, whether or not the tag moved.
Visible and hidden: splitting the rise
A shrinking package combines two changes, and it helps to see them separately. One is the visible change, the difference between the old and new price on the tag. The other is the size change, how much less the package holds. The real rise in the price per unit comes from both multiplied together. In the example, the tag rose 6.7% and the box shrank 14.4%. Because 18 ounces is about 1.169 times 15.4 ounces, the price per ounce rose by 1.067 times 1.169, minus one, which is 24.7%. The part of that rise you could see on the shelf was 6.7 points; the other 18.0 points were hidden in the smaller box. That split explains why shrinkflation feels different from an ordinary price increase. A shopper who notices prices, and many do, sees a modest 6.7% rise and may accept it. The larger part of the increase goes unnoticed unless the shopper checks the size. The pattern is even starker when the tag does not move at all. If the same box had shrunk to 15.4 ounces and stayed at $4.49, the whole 16.9% rise in the price per ounce would have been hidden, and the new price per ounce would have been about $0.292. The split also works in reverse. If a package shrinks while its price falls by more, the price per unit can actually drop, and nothing is hidden. And if a package grows, the size change works in the buyer's favor, so a higher tag can still mean a lower price per unit. This page reports each of those cases in its own words rather than calling every size change shrinkflation. The point of separating visible from hidden is not to judge a manufacturer's motives. It is to make sure the price you compare, against last year or against another brand, is the price for the same amount.
How the CPI handles smaller packages
A common suspicion is that shrinkflation lets inflation hide from the official figures. For the items it tracks, the Consumer Price Index is designed to catch it. The Bureau of Labor Statistics explained the method in a February 2023 Beyond the Numbers article on shrinkflation. For items whose size is reported, it calculates an effective price per standard size, usually a price per ounce, rather than using the price on the tag. Its example is a half-gallon, 64-ounce container of ice cream at $5.99 that is reduced to 60 ounces while the price stays at $5.99. The effective price per ounce rises from about $0.093 to about $0.0998, and the CPI records a 6.7% price increase, exactly the arithmetic this page performs. The agency's frequently asked questions describe the same principle for its data collectors. When the item they have been pricing changes in quantity, their example being a 64-ounce container of orange juice replaced by a 59-ounce one, they either select a new item or record the change so it can be taken into account. In other words, the CPI measures the price of a consistent amount of a product, not the price of whatever package happens to be on the shelf. That has two consequences for households. The first is that shrinkflation does count toward the inflation rate the CPI reports; smaller packages at the same price show up as higher prices in the index. The second is that the CPI still cannot tell you about your own basket. It averages across many products, stores and places, so the size changes in the brands you buy may be larger or smaller than the average. For your own purchases, the price per unit on this page is the measure to use, and the grocery inflation calculator can reprice a whole basket.
What smaller packages cost over a year
A few cents a package sounds trivial. Over a year of repeat purchases it adds up, and across a whole cart of items it can become a noticeable part of a food budget. This page puts a yearly figure on one product in two ways. The first asks what you pay beyond the old price per unit for what you now get. In the example, a household buying 24 boxes a year pays $114.96 instead of $107.76, while getting 369.6 ounces instead of 432.0. Priced at the old rate per ounce, those 369.6 ounces would have cost $92.19, so the household pays $22.77 more for the cereal it actually receives. The second asks what it would cost to keep eating as much as before. Replacing 432 ounces a year with 15.4-ounce boxes takes about 28.1 boxes, and the year costs $26.61 more than it used to. Which figure matters depends on whether your household ends up eating less or buying more. A few habits limit the damage. The most useful is reading the unit price on the shelf tag, which many stores print next to the price. Check that tags compare the same unit, since one product can be labeled per ounce and another per pound or per count. Compare across brands and store brands as well as sizes, because the brand that shrank is not always the most expensive per ounce afterward. Be careful with the assumption that bigger is cheaper. Larger packages are often cheaper per unit, but not always, especially when a smaller size is on sale. The unit price calculator settles that comparison for any two packages on the shelf. Finally, keep receipts or photos of the products you buy most. A record of the old size and price is what makes this calculation possible months later, when the new package has become the only one on the shelf.
Frequently asked questions
What is shrinkflation?
Shrinkflation is a price increase delivered by making a package smaller rather than, or as well as, raising the price on the tag. You pay the same or a little more and get less, so the price per ounce, sheet or count rises by more than the sticker suggests.
How do I calculate the real price increase when a package shrinks?
Compare the price per unit before and after. A cereal box that went from 18 ounces at $4.49 to 15.4 ounces at $4.79 cost about $0.249 an ounce before and $0.311 after. That is a real price rise of 24.7%, even though the sticker only went up 6.7%. The other 18.0 points of the rise are hidden in the 14.4% smaller box.
What if the price stayed exactly the same?
Then the whole increase is hidden. If the same box had shrunk from 18 to 15.4 ounces and stayed at $4.49, the price per ounce would have risen 16.9%, to about $0.292, with no change on the tag at all. At the old price per ounce the smaller box would sell for $3.84.
Does the CPI count shrinkflation?
Yes. The Bureau of Labor Statistics works from an effective price per standard size for items whose size is reported. Its own example, published in Beyond the Numbers in February 2023, is a half-gallon of ice cream at $5.99 cut to 60 ounces at the same price, which the CPI counts as a 6.7% increase in the price per ounce. So a smaller package at the same price shows up as inflation in the official figures.
How much does shrinkflation cost me in a year?
It depends on how often you buy. In the example, 24 of the smaller boxes a year cost $22.77 more than the old price per ounce would charge for the cereal you now get. To eat as much as before, you would need about 28.1 boxes a year, and the year would cost $26.61 more than it used to.
What if the package got bigger?
Then it is not shrinkflation, and the page says so. A larger package can cost more at the register and still be cheaper per unit, or cost more per unit despite the bigger size. The price per unit is the fair comparison either way.