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How Do I Identify a LEGO Part?

To identify a loose LEGO part, describe what you can measure — its colour, its basic shape, and its size in studs (the bumps on top) — and match that against the LEGO parts catalog. A 2×4 brick, for example, is two studs wide and four studs long. Once you know colour, shape, and size, only a handful of parts remain, and each one carries a part number you can use to find a replacement.

Here are the common ways to do it.

How are LEGO part sizes measured?

LEGO sizes are described in studs: width × length, sometimes with a height. Count the studs along each edge of the piece — that gives you the dimensions you'll search by.

• Good for: standard bricks, plates, and tiles where the studs are easy to count.
• Falls down on: curved, sloped, or oddly shaped pieces where "size" isn't a clean grid.

Browse a parts catalog by category

Open a LEGO parts database, pick a category (bricks, plates, slopes…), filter by colour, and scroll until you spot it.

• Good for: when you already know the rough category.
• Falls down on: categories are huge. Scrolling hundreds of grey plates to find the right one is slow, and you have to guess which category the part belongs to in the first place.

Ask a community

Post a photo to a LEGO forum or subreddit and let enthusiasts name it.

• Good for: rare or unusual parts that stump search.
• Falls down on: you have to wait, and it doesn't scale if you have a tub of mystery pieces.

The easy way: Afolio's Identify a Part tool PRO

Afolio lets you describe the piece and narrows the parts catalog as you go. Open Tools → Identify a Part (⌘⇧P) and set what you can see:

• Colour — pick one or more colours, with a separate toggle for transparent pieces of any hue.
• Shape — choose one family: brick, plate or tile, curved, round, wheel, window or door, panel, plant, animal, sticker, or Technic.
• Dimensions — type the stud dimensions. Order doesn't matter, so entering 2 and 4 finds a 2×4 part whichever way you measured it, and partial input still works — entering 2 and 4 matches both a 2×4 plate and a 2×4×3 brick.
• Attributes — toggles for Technic, curved, sloped, and where the studs sit (top, side, bottom).
• Name contains — a keyword if you know part of the name.

A live count updates as you add filters. When 100 or fewer parts match, a grid of candidates appears; click one to see its image, name, and part number, then Reveal in Catalog to open it. Copying the part number is one right-click away, ready to source a replacement from a pick-a-brick wall or marketplace.

Trying to recognise a whole set instead of a single piece? See how to identify a LEGO set. Working through a used set and need to know what's missing? Use the parts checklist.

Written by the Afolio team — practical guides from the makers of Afolio, the native Mac and iOS app for tracking a LEGO collection.

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