Introduction
The POSTNET (Postal Numeric Encoding Technique) barcode was invented by
US Postal Office to encode ZIP information. Having your letter printing
system POSTNET capable enables you to receive a discount on the postage.
The US delivery address coding can be of three forms (1) 5-digit ZIP; (2)
5-digit ZIP + 4 code (3) 11-digit delivery point code. So a valid POSTNET
barcode contains either 32 bars, 52 bars or 62 bars (including frame bars
and check digit, see below).
POSTNET is a numeric symbology. Different from most other symbologies, POSTNET has requirement to the actual bar height and width.
The information is encoded in the height and has nothing to do with the
spaces.
Check Digit Calculation
The check digit is based on Mod 10 algorithm. The value of the check
digit is that when added to the sum of other digits in the barcode, results
in a total that is multiple of 10. For example in the diagram above, the
check digit for 91801 is 1 since 9+1+8+0+1+1=20 which is two times of 10.
Structure of a POSTNET symbol
The POSTNET barcode starts with a long bar (frame bar) and ends with a
frame bar. Between these two frame bars is the encoded address information
followed by a check digit. Each code character is made up of five bars, either
long or short. If we use 1 to represent the long bar, 0 to represent the
short bar, each character is encoded based on the table to the left.
Barcode Locations
POSTNET barcode should be placed in lower right corner of the envelope
or in the address block as illustrated below. For more information, visit
US Postal Office web site.
Address block Barcode Placement Options
Web Tool
At barcode knowledge library we provide free web-based utilities for
readers to calculate check digits, performing number conversions. To
calculate Postnet check digit, refer to this page. If you have
purchased Morovia US Postal Font, you may consider checking out
this
page for additional utilities.
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