For GS1, the Basic UDI-DI (BUDI) is a Global Model Number (GMN). It identifies the device model or family. The article’s UDI-DI is a different GS1 key, the GTIN. Do not use the GTIN check-digit calculator to create a BUDI.
Prepare the two components
- Confirm your organisation’s assigned GS1 Company Prefix in its GS1 records. Do not guess its length from a GTIN.
- Choose a model reference under your company’s identification procedure. Confirm which devices belong to the group before assigning it.
- The prefix plus model reference may contain up to 23 characters. Two mandatory check characters complete the GMN: 25 characters maximum in total.
Calculate and check
Open the official GS1 GMN generator. Enter the prefix and model reference exactly, preserving upper- and lower-case letters. Calculate the check-character pair, then copy the complete GMN. If you already have the full code, use validation rather than calculating another pair on top of it. GS1 Italy also provides an official calculator with Calculate and Validate options.
If the code is rejected
- Format/length: check the issuer selected, prefix, model reference, allowed characters and total length. Remove accidental copying spaces.
- Check characters: check for missing final characters or a changed letter/case. Recalculate from the intended prefix and model reference; do not append a second pair.
A successful calculation does not verify prefix ownership, the correct device grouping or registration in EUDAMED. Save the complete GMN in your own records. UDI Studio prepares XML; it neither assigns the prefix nor automatically registers your BUDI. If the identifier is already registered, resolve a copying mistake against your records rather than inventing a replacement.