Rebrickable Help Guide: Part Numbering | Rebrickable

Part Numbering

Background and History

The Element ID is a unique, LEGO assigned part number, for a certain color, and/or a certain print if it has one. The most common LEGO part, the "Brick 2 x 4", is known in 59 different colors, and for each color there is at least one LEGO Element ID. Note that LEGO Element ID's have 6 or 7 digits. For example, the 2 x 4 Brick is known as a "3001" (Design ID, see below). A Black 3001 has Element ID 300126, and a Brown 3001 has Element ID 4124052. Note that Element IDs can be the Design ID followed by a color code (color code 26 in case of the Black 3001), but usually Element IDs are seemingly random numbers.

The Design ID is more complicated. Every mold of a part has the same Design ID, and that number is usually found molded into the part somewhere (mostly on the bottom). A LEGO Design ID typically has 4 or 5 digits. Where confusion comes in is for Printed parts. For example a 2 x 2 Brick has the Design ID 3003. This is molded into the underside on the brick. But if that 2 x 2 Brick has a print on it, then LEGO assign it a new Design ID. For example 3003pr0038 (which is a Rebrickable part number, more on that later) That is a 3003, 2 x 2 Brick and will have that number molded on it but Lego gave it Design ID 25660. Another complication with Design ID is when LEGO slightly change how they make the part. If the mold is slightly different, or they change a small detail about the part, they will assign it a new Design ID. To make things easier for LEGO builders most websites (including Rebrickable) combine these parts. On Rebrickable, if the change is considerable a new part is created and a mold relationship is attached to the part so users can find similar parts. This is why Rebrickable has multiple Design ID's connected to the same part.

A BOID is a BrickOwls inventory number. It is a random number and has has no meaning. Only BrickOwl use that number. It means BrickOwl ID.

On November 11th, 1993, a fellow by the name of Peter Miller compiled a first list of LEGO Design IDs, which would later be used in systems like LDraw, and for databases of Peeron, BrickLink and Rebrickable. However, many parts did not have a molded Design ID, and when those parts got entered into the Peeron system, they had to invent a new number, so they arbitrarily used an "x999" number. Similarly, when BrickLink entered it into their system, they also didn't know the appropriate number, but they also didn't co-ordinate with Peeron (or visa versa), and so they used a different "x999" number. In many cases, we still don't know the actual LEGO Design IDs of many parts, and these x-numbers are still present in our database. However, for more recent additions to our database and modern occurences of Lego not making a Design ID known, we have adapted to use the following designation 'upn' (Uknown Part Number) followed by a sequential 4-digit number, eg. upn0001. (Note: Certain themes use a slightly different upn designation to distinguish between certain Lego products, such as Duplo and Scala which use 'dupupn' and 'scalaupn' respectively).

Since about 2000, LEGO adds a parts inventory to the instructions booklet, and those inventories show all the Element IDs of the parts used.

When new parts are released, we create new part numbers for our inventorying needs. Our Rebrickable part numbers usually follow the first known Design ID, which is commonly the one molded on the part. When a part has a print we use the designation "pr" for Print, "pat" for Patterns (multicolored marbled parts), or "c0x" for pre-assembled parts, like Torsos, Arms, and Hands. Behind the designation we add a 4-digit sequence number. BrickLink uses an almost identical system, but their sequence numbers might be different. If BrickLink uses a different part number, we add a BrickLink mapping so the system will show the right link and translate the part number during import or export.

Determining a Part Number

When Submitting a Part, you need to provide a Part Numbers. Here are some guidelines on how to determine what part number to use:

For new parts, if you have the instructions booklet, start by finding the Element ID of the part, by checking the parts inventory in in the back of building instructions. Then search for the Element ID on Brickset.com, they will display the Design ID. They might also show a LEGO part description like "Mini Lower Part No. 1158." The number 1158 becomes the needed print number in this case.
When there is no Element ID known, or there is no info on it yet (this might occur for very new parts): we prefer not to pick a random unused number, because this might give problems later on, when a new part with that number in the Element ID info comes along, and they have get merged. For some parts, for example Minifig parts, where we can't find any info, we count down from 9999. The easiest way to find the lowest one, is to use the search bar. In this case, search on 970c00pr99. The auto-fill in starts here with part 970c00pr9920, so your next number will be 970c00pr9919.
And the last option, and the easiest of all: just show you don't know. You can submit the part as UNKNOWN or 970c00prXXXX, and we will find the correct number for you.

Copying Information from Other Sources

Unfortunately we cannot just accept information copied from another site such as BrickLink (other than Lego). Their numbering method and naming method are different to our own and often causes more confusion in the long run. Common errors that are made in this regard are using the word Pattern when referring to a Print (A Pattern on Rebrickable refers to multi-color injected parts like marbled parts) and using the designation 'pb' in the number.

Sticker Sheets

There is a standard naming system for Sticker Sheets. First to know is: On each (modern) Sticker Sheet is a number: yyyyy/xxxxxxx.
The part number for the Sheet will be the yyyyy section. The Element ID, that needs to be referenced in the submission, is the xxxxxxx section. This number is also often used in the BrickLink part name.
Naming is as follows: Sticker Sheet for Set aaaaa-1
Material = Plastic

If possible, please also include the BrickLink and BrickOwl number, so the export and import of the part into wanted lists works correctly. The easiest way to find these is by searching the part number or Element ID. The BrickOwl ID is called BOID in the part summation on BrickOwl

Exceptions on the rules:
When there are multiple sheets in 1 set: Sticker Sheet 1 for Set aaaaa-1
When the sheet is in multiple sets: Sticker Sheet for Sets aaaaa-1, bbbbbb-1

Other Considerations

Mold variations: Sometimes, a mold gets an update, without the mold number changing. In these case, we usually add a letter, starting with a for the oldest version. See for instance 4085a, 4085b and 4085c.
Prints and Patterns: If a part has a print, the base of the part number will be the mold number, followed by a print number. A print number is a prefix 'pr', followed by 4 digits. For instance, a print of 3001 will become 3001pr0001. The 4 digits are, when possible, based on the description that comes with the Element ID of the part. If the print number is unknown for all prints of the mold number, we just start at 0001. When there are also printed parts that can be based on the Element ID (for example 3626c Heads), we start at 9999 and count down, to avoid collision with the 'official' numbers. The same goes for Patterns. These are parts were an other color plastic is mixed during the molding process, like for instance 2546pat0001 Animal, Bird, Parrot Marbled Green Pattern. As you can see, patterns use the prefix 'pat', followed by 4 digits.
Assemblies: Some parts come pre-assembled. Examples are Hips&Legs and Torsos, where the arms and hands are already attached. These parts get a parts number, based on the main part in the assembly, followed by an assembly number, consisting out of an prefix 'c' and 2 digits. Hips&Legs for instance are 970c00. When there are more versions of the assembly, like different colored parts that are attached, the next becomes c01, etc.
Some non-buildable figures don't have an official number. These get a prefix, followed by 4 digits. The following prefixes are used, based on the category of the part:
- belfig - Belville Figures
- dupfig - Duplo Figures
- fabfig - Fabuland Figures
- fig - All other Figures
Then there are the parts where we just don't know. Sometimes because the number is lost in history, or because they just never got a number assigned. These parts get a prefix 'upn', which stands for Unknown Part Number, followed by 4 digits. Based on the category the part falls into, there can be a prefix before the 'upn'. Here is a list of prefixes in use:
- cardupn - Used for cards like playing cards and collectibles
- dupupn - Used for Duplo parts
- fabupn - Used for Fabuland parts
- stickerupn - Used for Sticker Sheets
- upn - Used for all other parts.

Last modified Sept. 29, 2025 by TobyMac

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HELP - Part Numbering

Part Numbering

Background and History

Determining a Part Number

Copying Information from Other Sources

Sticker Sheets

Other Considerations

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