About

Code 11 is a high-density numeric barcode symbology developed by Intermec in 1977. It encodes digits 0 - 9 and the dash character (−), producing compact labels used primarily in telecommunications equipment labeling and component identification. The symbology employs two modulo-11 check digits, designated C and K, making it more error-resistant than single-check symbologies. Incorrect check digit computation causes scanner rejection, halting inventory workflows and triggering manual audits. This tool computes both check digits algorithmically and renders the barcode with proper start/stop sentinels via Canvas, producing scanner-ready output.

Note: Code 11 is limited to the character set 0 - 9 and −. Data containing alphabetic or special characters cannot be encoded. The barcode density depends on the selected module width; scanners typically require a minimum module width of 7.5 mil (0.19 mm) for reliable reads at standard distances.

Formulas

The check digit C is computed over the original data characters. Let the data have n characters with values d₁, d₂, …, d_n.

C = ( n∑i=1 d_i × w_i ) mod 11

where w_i cycles through 1, 2, …, 10, 1, 2, … assigned right-to-left from the last data character. If the result equals 10, the check character is −.

K = ( n+1∑j=1 d_j′ × w_j′ ) mod 11

where the data for K includes the appended C digit, and weights cycle 1 - 9 right-to-left. The final barcode structure is: Start sentinel + data characters + C + K + Stop sentinel.

Where: d_i = numeric value of the i-th character (0 - 9 for digits, 10 for dash). w_i = positional weight. n = total number of data characters.

Reference Data

Character	Value	Bar Pattern (BSBSB)	Encoding (1=wide, 0=narrow)
0	0	00001	NNNNW
1	1	10001	WNNNW
2	2	01001	NWNNW
3	3	11000	WWNNN
4	4	00101	NNWNW
5	5	10100	WNWNN
6	6	01100	NWWNN
7	7	00011	NNNWW
8	8	10010	WNNWN
9	9	10000	WNNNN
−	10	00100	NNWNN
Start/Stop	-	00110	NNWWN
Check Digit Calculation Parameters
Check C	Weights cycle 1 - 10 right-to-left, modulo 11
Check K	Weights cycle 1 - 9 right-to-left (includes C), modulo 11
Module Dimensions (Industry Standards)
Narrow bar	1X (minimum 7.5 mil)
Wide bar	2X to 3X
Inter-character gap	1X
Quiet zone	≥ 10X each side
Typical density	15 char/inch at 7.5 mil
Max data length	No formal limit; practical limit ~40 chars

Frequently Asked Questions

Code 11 achieves approximately 15 characters per inch, making it denser than Code 39 (roughly 9 characters per inch). However, Code 11 only encodes digits 0 - 9 and the dash character, while Code 39 supports full alphanumeric and Code 128 supports the full ASCII set. Code 11 was designed specifically for telecom equipment labeling where only numeric identifiers are needed and label space is limited.

The Code 11 specification requires check digit C for all barcodes. The second check digit K is mandatory when the data length (excluding check digits) is 10 characters or more. For data shorter than 10 characters, a single check digit C may suffice, but best practice is to always include both for maximum error detection. This generator always computes both.

When the weighted sum modulo 11 produces 10, the check character is the dash symbol (−), which has a value of 10 in the Code 11 character set. This is the only non-numeric character in the symbology and serves dual purpose as both a data character and a potential check digit value.

The quiet zone (blank space) on each side of the barcode must be at least 10 times the narrow module width (10X). At a typical X dimension of 10 mil, each quiet zone must be at least 0.1 inches (2.54 mm). Insufficient quiet zones are the most common cause of scan failures in production environments.

Most retail POS scanners are configured to read Code 128, EAN/UPC, and Code 39 by default. Code 11 decoding is typically disabled and must be explicitly enabled in the scanner configuration. Industrial scanners used in telecom and warehouse environments usually support Code 11 natively. Verify your scanner model supports USD-8 (the ANSI designation for Code 11) before deployment.

Code 11 uses a wide-to-narrow ratio between 2.0:1 and 3.0:1. A ratio of 2.5:1 is recommended for optimal print tolerance. Ratios below 2.0:1 make wide and narrow elements too similar, increasing misread rates. Ratios above 3.0:1 unnecessarily increase barcode width without improving readability.