CalcWhenBarcode Generator — Code 128
The text HELLO-128 becomes a real Code 128 barcode below — start symbol, data, a modulo-103 checksum and stop symbol — ready for a scanner to read back exactly.
How it works
Code 128 is the workhorse barcode of warehouses, libraries and asset tags: compact, able to encode ordinary text, and protected by a checksum so a misread fails loudly instead of silently changing your data. Type anything printable — a SKU, a serial, a name — and the barcode renders with its human-readable text beneath, the way labels are actually printed.
Print it, stick it, scan it with any standard scanner or phone barcode app to prove it round-trips.
The method
Code 128 set B per ISO/IEC 15417: start-B symbol (104), one symbol per character (ASCII 32–126 mapped to values 0–94), checksum = (104 + Σ value×position) mod 103, stop symbol (106), drawn from the standard bar/space width table as a resolution-independent vector.
Frequently asked questions
Is this a UPC I can put on products for shops?
No — retail UPC/EAN codes are issued numbers from GS1 with their own format. This is Code 128, the right choice for your own inventory, assets, shelves and internal labels, where you control the numbering.
What characters can it encode?
Set B covers standard keyboard text: letters (both cases), digits, spaces and common symbols — ASCII 32 to 126.
Why does the barcode include a checksum?
So scanners can catch errors: the check digit is recomputed from the scanned data and must match, or the read is rejected rather than recorded wrong.