Lego bricks are built on an 8 mm grid. One stud takes up 8 mm, a brick is 9.6 mm tall without its stud, a plate is 3.2 mm, and every part is 0.2 mm shorter than its grid, so a 2 × 4 brick measures 31.8 × 15.8 × 9.6 mm plus about 1.7 mm of stud.
Those are the nominal dimensions, the ones Lego designs to and the ones that add up when you plan. Real bricks deviate from them by fractions of a millimetre, and the published references do not all agree on the stud itself. We keep the two apart below: first the design numbers and conversion charts, then what measurements and Lego's own documents say about tolerances.
Lego dimensions at a glance
| Dimension | Nominal size | In inches | Note |
|---|---|---|---|
| Stud pitch (centre to centre) | 8.0 mm | 0.315 in | The basic grid unit |
| Width of a 1 × 1 brick or plate | 7.8 mm | 0.307 in | 8 mm minus 0.1 mm on each side |
| Brick height without stud | 9.6 mm | 0.378 in | Three plates |
| Plate height without stud | 3.2 mm | 0.126 in | One third of a brick |
| Stud diameter | 4.8 mm | 0.189 in | Measured studs come out at about 4.9 mm |
| Stud height | about 1.7 mm | about 0.067 in | References give 1.6 to 1.8 mm |
| 2 × 4 brick | 31.8 × 15.8 × 9.6 mm | 1.25 × 0.62 × 0.38 in | Without studs |
| Duplo brick | twice every dimension | twice every dimension | A 2 × 4 Duplo brick is about 64 × 32 × 19.2 mm |
The 8 mm pitch is the number everything else hangs on. A brick or plate is always a whole number of studs long and wide, and its outer length is that number times 8 mm, minus 0.2 mm. The missing tenth of a millimetre on each side leaves room between neighbouring bricks. When a brick is pressed onto studs, its walls flex outwards a little, and without that gap the bricks in a wall would push each other apart.
Heights follow a different rule. A brick is 9.6 mm tall, which is 1.2 times the stud pitch, so a 1 × 1 brick is not a cube. Lego's own support pages put it the simple way: three plates stacked on top of each other are exactly as tall as one brick. If terms such as stud, tile or baseplate are new to you, our Lego glossary explains them.
Lego A/S gives the same figures in its own patent text: a 2 × 4 brick about 3.2 cm long, 1.6 cm wide and 0.96 cm high without the studs, with studs about 0.48 cm across. A Duplo brick is twice the size in all three directions, at about 6.4 × 3.2 × 1.92 cm with 0.96 cm studs.
Studs to mm, cm and inches
Two lengths matter when you convert. The grid length, studs times 8 mm, is the space a section takes up in a larger build and the distance between parts on the same plate. The part length, grid minus 0.2 mm, is what you measure with calipers on a single brick or plate.
| Studs | Single part (mm) | Grid length (cm) | Grid length (inches) |
|---|---|---|---|
| 1 | 7.8 | 0.8 | 0.31 |
| 2 | 15.8 | 1.6 | 0.63 |
| 3 | 23.8 | 2.4 | 0.94 |
| 4 | 31.8 | 3.2 | 1.26 |
| 6 | 47.8 | 4.8 | 1.89 |
| 8 | 63.8 | 6.4 | 2.52 |
| 10 | 79.8 | 8.0 | 3.15 |
| 12 | 95.8 | 9.6 | 3.78 |
| 16 | 127.8 | 12.8 | 5.04 |
| 24 | 191.8 | 19.2 | 7.56 |
| 32 | 255.8 | 25.6 | 10.08 |
| 48 | 383.8 | 38.4 | 15.12 |
The other way round is just as quick. Multiply centimetres by 1.25 to get studs, because 10 cm is exactly 12.5 studs. One inch is about 3.2 studs, a foot about 38 studs, and a metre is 125 studs. Round down when the result has to fit into a gap, and round up when the build has to cover something.
Heights in plates and bricks
| Stack | Height without top stud | In inches |
|---|---|---|
| 1 plate | 3.2 mm | 0.126 in |
| 2 plates | 6.4 mm | 0.252 in |
| 1 brick (3 plates) | 9.6 mm | 0.378 in |
| 2 bricks | 19.2 mm | 0.756 in |
| 5 bricks | 48.0 mm | 1.890 in |
| 10 bricks | 96.0 mm | 3.780 in |
Add the stud only once, on top of the stack: a column of ten bricks is 96 mm plus about 1.7 mm. Thinking in plates makes height planning easier, because every brick is three plates and every height in a model is a whole number of plates, apart from a few special parts.
Five bricks stacked are 48 mm tall, exactly as wide as six studs. That 5:6 ratio between brick height and stud width, or 6:5 the other way round, is why a tower of bricks never matches its own footprint, and it is the starting point for building sideways.
SNOT: making sideways parts line up
SNOT stands for "studs not on top": parts turned on their side or upside down so that their studs face outwards. For sideways sections to sit flush with the rest of a model, their thickness has to match a whole number of studs. These are the combinations that do:
| Sideways stack | Height | Matches |
|---|---|---|
| 1 brick + 2 plates (or 5 plates) | 16.0 mm | 2 studs |
| 5 bricks (15 plates) | 48.0 mm | 6 studs |
| 1 plate + 1 tile + the thin upright of a bracket | 8.0 mm | 1 stud |
The first row is the one you will use most: two studs equal five plates. It works for every even number of studs. Odd numbers are where it gets tricky, because one stud equals two and a half plates, and plates do not come in halves. The half plate usually comes from the thin vertical part of a bracket, which is half a plate thick.
Jumper plates solve the same problem across the grid. Their single centred stud shifts whatever sits on top by half a stud, 4 mm, which lets you centre a 1-stud-wide detail on a 2-stud-wide surface.
Technic bricks follow the 5:2 rule as well. Stack a Technic brick, two plates and another Technic brick, and the holes end up 16 mm apart, two studs, so a Technic beam can brace the stack vertically. One detail catches people out: the pin holes in Technic bricks sit about 0.2 mm higher than the exact centre of a brick, to leave room for studs underneath. Studs pushed into those holes are therefore slightly off compared with a dedicated brick with a stud on its side. In a static model you rarely notice. Next to panels mounted on proper SNOT bricks, though, it can show as a small step.
Diagonals work with whole studs only in a few combinations. The classic one is the 3-4-5 triangle: a brace that spans 3 studs in one direction and 4 in the other is exactly 5 studs long, and the 6-8-10 triangle works the same way.
Planning a build, a shelf or a MOC in studs
Plan in studs and plates first, and convert to centimetres or inches at the end. A sheet of squared paper with one square per stud, and a separate note of heights in plates, is enough for most MOCs. Digital tools based on the LDraw parts library use their own unit: 1 LDU is about 0.4 mm, so a stud is 20 LDU wide, a brick 24 LDU tall and a plate 8 LDU. Those whole numbers keep every position on the grid. If your project is a MOC of your own, our guide to Lego MOCs covers where to start.
Some common footprints, worked out:
- Modular buildings: they stand on a 32 × 32 baseplate, which is 25.6 cm on the grid. Lego gives its 32 × 32 baseplate as over 25 cm square. A finished building can be wider than its plate where balconies, signs or cornices stick out: Lego lists Tudor Corner 10350 at over 26 cm wide. Our guide to choosing a first Lego modular building compares the stated sizes.
- Speed Champions cars: since 2020 they are 8 studs wide, 6.4 cm on the grid, instead of the earlier 6 studs (4.8 cm). Mirrors can stick out a little beyond that.
- Trains: City-style trains are 6 studs wide, while many display trains are 8. In our experience, 8-wide wagons do not fit through a station designed for narrower trains, so plan platforms, tunnels and bridges for the widest train you own.
- 48 × 48 baseplate: 38.4 cm on the grid, one and a half modular footprints.
For shelves and cases, start from Lego's stated size of the finished model, not from the stud count of its base. The stated size includes everything that overhangs. Our guide to Lego display shelves works through depth and height for common models.
Tolerances: what the nominal numbers do not tell you
Every figure in the tables above is nominal. Real bricks are close but not identical, and careful measurements show it:
| What was measured | Nominal | Measured |
|---|---|---|
| Stud pitch, across a wall of Technic beams at 25 °C | 8.0 mm | 7.986 mm |
| Brick height, derived from the same series | 9.6 mm | 9.582 mm |
| Plate height, derived from the same series | 3.2 mm | 3.194 mm |
| Stud diameter, bricks from the 1960s to recent sets, micrometer | 4.8 mm | 4.87 to 4.90 mm |
| Width of 2 × 4 bricks, same micrometer series | 15.8 mm | about 15.9 mm |
| Length of 2 × 4 bricks, same micrometer series | 31.8 mm | about 31.9 mm |
The studs are the interesting case. Measured studs are consistently around a tenth of a millimetre larger than the 4.8 mm design value, and that is plausibly deliberate: a slightly oversized stud forces the walls of the brick above to flex, and that flex is what Lego calls clutch power. Some references round the stud to 5 mm for the same reason. Stud height also varies between sources, from 1.6 mm to about 1.8 mm, and vertical measurements depend on how firmly the bricks are pressed together.
We have not found a production tolerance for Lego's moulds in anything Lego publishes. Very small figures circulate online, but none of them traces back to a statement from Lego, so we do not repeat them here. The closest thing in Lego's own documents is the patent text quoted above, which says that these dimensions may vary by at most 1 % for elements to stay compatible and connectable. On a 32 mm brick, 1 % is about 0.3 mm. That is a definition of what still counts as compatible, not the precision of a production mould.
Duplo follows the same logic at double the scale. According to Lego, only Lego pieces with an even number of studs fit Duplo, such as a 2 × 2 or 2 × 4 brick, while a 1 × 2 or 2 × 3 brick does not. Lego bricks also sit on Duplo bricks that have hollow studs.
Clone bricks and other brands
Regular bricks from other brands use the same 8 mm grid. In our own building, the grid is almost never the problem; the clutch is. Third-party bricks are often a little too loose or a little too tight, and some sets mix both. With plates that hold minifigures, we have swapped loose third-party plates for Lego plates after figures kept falling over. The large 50 × 50 BlueBrixx baseplates hold about as firmly as Lego's in our experience, but they are slightly thicker, which shows when you lay them next to Lego baseplates.
Our comparison of BlueBrixx and Lego goes further into fit, and it also explains why BlueBrixx Diamond Blocks are a smaller system that does not connect to regular bricks. Lumibricks describes its bricks as compatible with Lego System dimensions, which is the maker's own claim; our Lumibricks guide looks at what that means for its lighting parts. When we fill colour gaps in a MOC with parts from other brands, the dimensions line up; test clips, hinges and Technic connections before you rely on them in anything that moves or carries weight.
Lego brick dimensions FAQ
How big is a Lego brick in mm?
A standard 2 × 4 brick is 31.8 mm long, 15.8 mm wide and 9.6 mm tall without its studs. The studs add about 1.7 mm on top. A 1 × 1 brick is 7.8 × 7.8 × 9.6 mm.
How many plates make one brick?
Three. A plate is 3.2 mm tall and a brick 9.6 mm, and Lego states that three stacked plates are exactly as tall as one brick.
How many Lego studs are in an inch or a centimetre?
One inch is about 3.2 studs, and one centimetre is 1.25 studs. To convert a length in centimetres to studs, multiply by 1.25; for inches, multiply by 3.175.
Are Duplo bricks twice the size of Lego bricks?
Yes, in all three dimensions. A Duplo stud has the pitch of two Lego studs, which is why Lego pieces with an even number of studs connect to Duplo and odd-numbered ones do not.
The numbers to remember
- 8 mm per stud, and every part is 0.2 mm shorter than its grid.
- 9.6 mm per brick and 3.2 mm per plate, three plates to a brick.
- 2 studs = 5 plates and 6 studs = 5 bricks for sideways building.
- Studs × 0.8 gives centimetres, centimetres × 1.25 gives studs.
- Plan shelves and cases from Lego's stated model size, not from the stud count of the base.
