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 2x4 brick and a DUPLO 2x4 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 Above and below a DUPLO 2x2 brick one can put two LEGO 2x4 bricks (or four 2x2 LEGO bricks). The outer walls of such stack seem to align perfectly, so the width and length of a DUPLO 2x2 brick is equal to the width of a LEGO 2x4 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*√2 - 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: 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 can be derived from wall width and stud outer diameter.
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. For the short answer, Duplo studs are indeed taller than twice the height of a Lego stud. And don't rely too heavily on measurements you get from ldraw (and not just for Duplo). For a really long-winded history on this... First, note that when I authored the original Duplo parts I never actually measured them with a ruler or calipers, as there was no need. The ldraw system assumes "perfect" dimensions in terms of other ldraw parts, so you typically measure parts by comparing them to other Lego pieces. By this measurement, Duplo in ldraw (not counting the studs) is exactly twice the size of Lego. In real life, any part is slightly smaller than the nominal measurement so that you can slide two parts next to each other without them hanging up on each other.
Duplo parts seem to be about twice as tolerant in this way, so I'd guess that in real life also the outer dimensions are very close to twice the size. Some time in the 1990's, Duplo studs were changed. They were made taller, and the inner hole got larger (making the stud walls thinner). They also added bumps to the inside of the stud hole. The ldraw Duplo stud has the taller height of the new stud and the perfect roundness and dimensions of the old stud hole. Regular Lego bricks used to have smooth internal walls, and the ldraw bricks still look like this. Duplo bricks always had "splines" that run vertically along the inside walls for Duplo studs to clutch. Regular Lego studs clutch against the outer wall of the Duplo brick instead. This is how studs of different sizes can both fit into the underside of a Duplo brick. Lego started making the walls of regular Lego look like Duplo bricks. I assume this is a cost-cutting measure where they now use less plastic to mold the walls, but now have splines like Duplo so that the walls are the old thickness in the places where studs need to clutch.
Duplo wall thickness is the same as Lego wall thickness from before 2003 or so. It's 4 LDU (ldraw units) if that helps. For reference, a plate is 8 LDU high without the stud, and a 1x1x1 brick is 20x20x24 LDU without the stud. Studs in ldraw are 4 LDU high, but that is totally inaccurate. Non-hollow studs are clearly more than half the height of a plate, and the real height of regular studs should be more like 4.25 LDU. Be very wary of the measurements that you get from parts converted from ldraw format to POV-Ray. L3P scales each part down just a little bit to let POV-Ray show edge lines. There is no simple real-world conversion from ldraw units to inches or centimeters. Primo is another story... Did you find this question interesting? Sign up for our newsletter and get our top new questions delivered to your inbox (). This is not a full answer, but the Free Art and Technology Lab seems to have carefully measured a DUPLO brick as part of the Free Universal Construction Kit.
The parts are made available as STL file, for instance /thing:15945 - includes DUPLO upper side /thing:15924 - includes DUPLO bottom side Maybe someone knows how to get the precice dimensions from the STL file. There is another DUPLO brick at Thingiverse which seems to be less precise. At least one can get the numbers from the OSCAD file.Browse other questions tagged piece-information size duplo or ask your own question.For the Kinder Duplo confectionery product, see Kinder Chocolate. Duplo (trademarked as DUPLO) is a product range of the construction toy Lego, designed for children aged 1½ to 5 years old. Duplo bricks are twice the length, height and width of traditional Lego bricks, making them easier to handle and less likely to be swallowed by younger children. Despite their size, they are still compatible with traditional Lego bricks. Initially launched in 1969, the Duplo range has gone on to include sets with figures, cars, houses and trains. Duplo is manufactured in Nyíregyháza, Hungary.
Duplo bricks alongside a smaller red regular-sized Lego brick Duplo and regular-sized Lego compatibility demonstrated Duplo bricks were introduced in 1969, in four colors: red, yellow, blue, and white. The following year, two more sets were added with blue and red wheel plates. In the product catalog for 1971, the sets were described as being for children from 1 to 2 years, but were still sold mixed with Lego bricks, normally designed for ages 3 to 12. In 1972, the Duplo brick with two rows of two studs was introduced. In 1975, Duplo became its own product brand, with five sets made up exclusively of Duplo bricks. New additions included a round-topped two-by-two stud brick and a small four-wheeled wagon with two rows of six studs. With these new Duplo sets, Lego began targeting children 1½ years old with the intention that when the children became older, their Duplo bricks could be used together with regular Lego bricks. In 1977, the Duplo name was dropped in favor of Lego Preschool.
Small figures the size of two-by-two bricks were introduced, made up of a cylindrical head and a tapered, limbless body, similar in design to Fisher-Price's Little People. Another new brick was a half arch. The new sets included figures, doors, and two-by-six brick wagons that could act as a car or train. The name Duplo was brought back in 1979, along with a new reworked logo. Some brick sets were sold inside a plush version of the rabbit from the logo, that zipped closed. In 1983, other Duplo figures appeared, often called Duplo people. These figures have a moveable head, arms, and legs and look like large Lego minifigures, but cannot be taken apart, making them safer for small children. Also in 1983, set number 2700 was introduced with a model of a steam engine with two train cars. In 1986, a Duplo doll house with sliding doors was introduced. This included a Duplo people mother, father, and smaller child. In 1992, Duplo Toolo was introduced. These used internal screws to stay together.