How does UPC-E conversion work?
UPC-E represents a qualifying UPC-A number in eight printed digits. Expanding it restores the full twelve-digit UPC-A before checking the final digit. Both representations identify the same item.
Worked example
The compression mode digit
UPC-E has a number-system digit, six data digits and a check digit. The sixth data digit, immediately before the check digit, selects the expansion rule.
Here, the blue 0 moves after the first two data digits. Four zeros are restored before the remaining three data digits. The green 7 stays as the check digit.
- Mode 0, 1 or 2
Move the mode after the first two data digits, restore four zeros, then append the remaining three.
- Mode 3
Keep the first three data digits, restore five zeros, then append the next two.
- Mode 4
Keep the first four data digits, restore five zeros, then append the fifth.
- Mode 5 to 9
Keep the first five data digits, restore four zeros, then append the mode digit.
The number-system and check digits stay at the ends. Compression works only when reversing one of these rules reproduces the original UPC-A exactly.
Enter UPC-E
Enter all eight printed digits, including the first and final digits.
Expand and validate
Restore the full UPC-A number and check its final digit.
Convert back
A qualifying UPC-A number can be compressed to UPC-E.
Both forms identify the same item and keep the same check digit: 7.
GS1 zero-suppression rules