Linear symbology
UPC-E
UPC-E is a compressed form of UPC-A that prints six data digits instead of eleven by suppressing runs of zeros in the original number. It exists for small retail packs, and only UPC-A numbers with a qualifying pattern of zeros can be expressed in it.
Specification
These are the values the editor enforces while you design, not figures collected from elsewhere — the same numbers its quiet-zone and resolution checks run on.
| Property | Value | In context |
|---|---|---|
| Minimum X-dimension | 0.264 mm | 0.0104 in · 10 thou |
| Quiet zone | 9 modules | 2.38 mm at the minimum X-dimension |
| Dimensionality | Linear (1D) | Read by laser or imager |
UPC-E at 203, 300 and 600 dpi
A printer can only place whole dots, and 0.264 mm is not a whole number of them at any of these resolutions. What changes is how much a single dot of rounding costs you as a share of the narrow bar.
| Resolution | Narrow bar in dots | Printed as | Rounding error |
|---|---|---|---|
| 203 dpi | 2.11 | 2 dots | 5% |
| 300 dpi | 3.12 | 3 dots | 4% |
| 600 dpi | 6.24 | 6 dots | 4% |
What UPC-E encodes
Seven or eight digits as entered — a number system digit, six data digits and the check digit. The symbol printed is the zero-suppressed form; a scanner expands it back to the full 12-digit UPC-A before passing it to the till.
Where it is used
- Small retail packs where a full UPC-A will not fit at its minimum size
- Single-serve and travel-size products in North American retail
Check digit
The check digit is calculated from the expanded 12-digit UPC-A number, not from the six digits printed in the compressed symbol. That is why the digit shown under a UPC-E cannot be derived from the digits beside it.
How UPC-E fails in practice
- Assuming any UPC-A can be compressed. Only numbers with a qualifying pattern of zeros in the manufacturer and item fields have a UPC-E form at all.
- Computing the check digit from the visible six digits rather than from the expanded number, which produces a symbol that scans to the wrong product.
When to use something else
Questions about UPC-E
- Why will my UPC-A not convert to UPC-E?
- Zero suppression only works on numbers with particular patterns of zeros in the manufacturer and item reference fields. Most UPC-A numbers do not qualify, and there is no way to force one that does not.