Basic UDI-DI (GMN) check character calculator
Enter your model number and we calculate the two check characters to append to the GMN; or enter the full GMN and we tell you whether the check pair is correct. Every line is evaluated separately, so you can paste a whole column.
One value per line. Case matters; a space is not a valid character. A leading (8013) prefix is recognised and removed.
The calculation runs only in your browser; the values you enter are not sent to any server.
Results appear here. A GMN has at most 25 characters including the check pair and starts with a GS1 company prefix.
A correct check pair only shows there is no typo. It does not verify that the GMN was properly allocated under your GS1 company prefix or matches your EUDAMED record; this tool is not an official verification by GS1 or any authority.
If you would like to review your Basic UDI-DI and UDI-DI master data, label templates and registration process together, get in touch.
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How to use it
A
Choose the action: calculate the check pair, or verify an existing GMN.
B
Type the GMN data (or the full GMN) or paste a column; every line is evaluated separately.
C
For a single value the calculation is shown character by character; for many lines, copy the results and paste them back into your sheet.
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What is a Basic UDI-DI and what does it do in EUDAMED?
A Basic UDI-DI identifies a group of devices with the same intended purpose, the same risk class and the same essential design and manufacturing characteristics. It is the main key of a device record in the UDI database and in EUDAMED; records for the declaration of conformity, certificates and technical documentation are linked to it. That is why the value must be correct and unambiguous in your master data.
The Basic UDI-DI does not appear on the label or packaging and is not encoded in the barcode. What is on the label and in the barcode is the packaging-level UDI-DI and the production identifier (UDI-PI).
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How it differs from the UDI-DI and how it relates to the GMN
A UDI-DI identifies a specific device and packaging level; in the GS1 system it is a GTIN. The Basic UDI-DI sits one layer above: under one Basic UDI-DI there can be many UDI-DIs for different packaging levels, sizes or variants. For the definition of the Basic UDI-DI and when it changes, see MDR (2017/745) Annex VI and MDCG 2018-1.
For the Basic UDI-DI, GS1 uses the Global Model Number (GMN, application identifier 8013). A GMN starts with a GS1 company prefix, followed by model characters the manufacturer chooses, and ends with two check characters. The total length is at most 25 characters, drawn from the CSET 82 character set: digits, upper- and lower-case letters and a few punctuation marks.
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How are the two check characters calculated?
The CSET 82 value (0–81) of each data character is multiplied by a weight. The weights are prime numbers counted from the right: the last data character gets 2, its left neighbour 3, then 5, 7, 11 … (for the maximum of 23 data characters the largest weight is 83). The sum of the products is divided by 1021 and the remainder is a number between 0 and 1020.
The integer quotient of that number divided by 32 gives the first check character and the remainder the second; both are taken from the CSET 32 character set (digits 2–9 and the letters except I and O, to avoid confusion with 1 and 0). The calculator was tested against the example GMN in the GS1 General Specifications: for 1987654Ad4X4bL5ttr2310c the check pair is 2K.
FAQ
- Are the values I enter sent anywhere?
- No. The calculation runs entirely in code inside your browser; the values are neither transmitted to a server nor stored.
- Is a GMN the same as a Basic UDI-DI?
- For manufacturers using GS1, yes: the Basic UDI-DI is formed as a GMN. If you chose another issuing entity, the format of the Basic UDI-DI follows that entity's rules.
- Which characters can a GMN contain and how long can it be?
- CSET 82 characters: digits, upper- and lower-case letters and the marks ! " % & ' ( ) * + , - . / : ; < = > ? _ . Upper and lower case are different characters. At most 25 characters including the check pair; the beginning is your GS1 company prefix.
- If the check pair is correct, is the GMN valid?
- No — it only shows that there is no typo. Whether the GMN was allocated under your company prefix and matches your EUDAMED record has to be checked separately.
- Why does the Basic UDI-DI not appear on the label?
- The label and barcode carry the UDI-DI specific to the device and packaging level plus the UDI-PI. The Basic UDI-DI is used on the registration and certification side; see MDR Annex VI for details.
UDI master data and labelling: consistent?
In our serialization and labelling projects we tie GMN, GTIN and SSCC validation to master data entry, so a wrong value is caught before it reaches a record or a label.