What that Bar Code Really Means

On Friday, Kellogg’s recalled about 28 million boxes of cereal because consumers reported an unusual smell coming from the packaging that could potentially make people ill. In order to help identify the specific products involved, Kellogg’s referred the public to the universal product code (UPC). That’s the official name for the pattern of black lines on the side of almost everything you can possibly purchase. Simply put, the bar code.

This code reveals our purchasing habits to manufacturers, retailers and credit card companies. Most complaints about the erosion of privacy through technology revolve around these little scannable designs.

What makes the bar code interesting is that the lines as well as the 12-digit code have meaning. The white spaces between the black lines are also meaningful. The bars are for machines to “read,” the numbers for us unsophisticated humans. We’ll get to the bars in a bit.

The first six numbers are related to the manufacturer and the type of transaction, the next five describe the product or item number. The last number is the checkdigit, which is used to validate that all of the other numbers have been read correctly by a scanner. The calculation for validation is elaborate (if you want proof, have a crack at it)

The first number, set off from the rest on the left, designates the general nature of the purchase; coupons, pharmaceuticals, or special pricing arrangements made within the store among other possibilities. The next five numbers, grouped together, are the specific manufacturer ID. The next three are called the family code, and the two digits before the checkdigit are the value code. The family code describes a family of products, while the value code designates the value or nature of a coupon.

Now, the bars. (This is a very general explanation of a mathematically complex system. If you seek greater detail, look here.)

Notice that there are four different widths of bar in any UPC code. Each of the four sizes corresponds to a value of one to four. So a black line followed by a white line followed by another black line is three “ones.” This is how all UPC codes begin. After this “start code,” every sequence of 4 line widths corresponds to binary code for one of the numbers that appear beneath the bars. The last three digits are once again three “ones.”

So let’s try to understand the UPC of one of Kellogg’s recalled cereals, 3800039132 3. First, note that Kellogg’s only provides 11 out of 12 numbers. Referencing above, we can determine that’s because the first number is always specific to the type of transaction that will be used to purchase the product. Since Kellogg’s doesn’t include that initial digit (set off from the rest, like the checkdigit), the recall is too broad to specifiy by transaction type. The five numbers “38000″ are Kellogg’s manufacturer ID number. The “391″ specifies the identity of the Kellogg product, and the “32″ is a value code that explains the nature of any coupon deals associated with the product.

Returning to English, this UPC is basically saying “I’m an 8.7 ounce box of Apple Jacks.”

Per this specific recall, other factors besides the UPC are necessary to help you determine whether a particular box of cereal is part of the recall or not. For more information, check out Kellogg’s Web site.


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