The dimensions of LEGO brick are documented well, but what about DUPLO bricks? If have only found the general statements that DUPLO is twice as large as LEGO but no exact numbers. What about the thickness of walls and the space that must be subtracted at each side (0.2mm for LEGO), is it also just doubled?. If you compare the bottom of a LEGO 2×4 brick and a DUPLO 2×4 brick, there are also additional small walls that I have not found documented.

*Update:* Some dimensions of a DUPLO brick can be derived from the dimensions of a LEGO brick, which have been documented by Robert Cailliau among

others:

Above and below a DUPLO 2×2 brick one can put two LEGO 2×4 bricks (or four 2×2 LEGO bricks). The outer walls of such stack seem to align perfectly, so the **width** and **length** of a DUPLO 2×2 brick is equal to the width of a LEGO 2×4 brick, which is **31.8mm** (32mm-0.2mm). By putting DUPLO and LEGO side by side, one can also see that the DUPLO **height** without studs is twice of the size in LEGO (**19.2mm**). The LEGO studs below the DUPLO brick touch DUPLO walls, so DUPLO **wall thickness** is the same as LEGO wall thickness (either before spline walls were introduced to LEGO bricks or LEGO wall thickness plus the length of LEGO splines), which is **1.5mm**. The DUPLO **tube height** is the height of the brick minus the height of a LEGO stud (which is somewhere between 1.6mm and 1.8mm). I’d better use the larger value, so the tubes start 1.8mm above the floor of the brick. From the top, LEGO tubes fit into DUPLO studs, so the **stud inner diameter** should equal to **6.51mm** (8*â2 – 4.8$). But if you carefully look inside a DUPLO stud, this fitting is only achieved by four additional lugs that give a minimal inner diameter around 6mm to facilitate snapping into.

The remaining dimension include:

- stud outer diameter
- stud height
- tube inner diameter (but DUPLO tubes are not fully circular inside

on a closer look!)
- tube outer diameter (also occurs at some other elements for instance as stem at #6510)
- spline length

Spline length can be derived from wall width and stud outer diameter. Tube

outer diameter and stud outer diameter can also be computed from each other. So basically three dimensions are left to be explained. Comments and insights are welcome how more of the remaning dimensions can be

derived from standard LEGO/DUPLO dimensions.