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august 10th, 2002.

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access to my Lego pages since creation.

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Copyright 1996, 2000, Denis Cousineau


Lego Brick measurements.

Height, width, and weight

In the following sections, torque of a Lego motor and strength of pneumatics are all measured using Lego bricks as weight. It is therefore necessary to know their dimension and their weight.

The standard 4 ´ 8Lego brick is constructed as follow:

4 X 8 brick with measurements

A 1 ´ 1 Lego bricks can also be measured in terms of bump:

Width   1 bump 0.80 cm
Height   1.2 bump 0.96 cm
Height of a plate   0.4 bump 0.32 cm

As seen, one brick and two plates on top of each other equal 1.2 + 2 ´ 0.4, or 2 bumps (or equivalently in cm: 0.96 + 2 ´ 0.32, or 1.60 cm). This represents exactly 2 bumps high, so that a beam on the side can connect nicely with horizontal beams separated by two plates.

Its weight is 2.5 grams each standard Lego brick. With 400 of them, you have exactly a kilogram (that is, approximately 2.2 lb).


The new beams are very convenient, but also composed of a weird angle. If you place them on a wall, as shown below, we see that the 1-angle beam is adjusting perfectly over holes located at 3 bumps on the horizontal and 4 bumps on the vertical. This is a triangle with sides 3-4-5, as you certainly remember from your trigonometry courses. What is less known is that this triangle forms an angle of 36.87° (you can check this by noting that cosine of 36.87 is 0.8, or 4 bumps for a radius of 5 bumps; similarly, sine of 36.87 is 3/5, or 0.6). The two-angle beams are simply composed of 45° angles, easier to manage...

angles.gif (57768 bytes)

Method of measurement.

Of course, it is merely impossible to take one brick, and arrive to the above precision. The most accurate technique to measure small things is to measure a lot of them, and then divide by the number of measured objects. To measure the length of a brick, I noted that in 1 meter (100 cm), exactly 125 bumps could be assembled side to side. This lead to the simple calculation that 1 bump is 4 fifth of a cm, or 0.8 cm. Similarly, in a meter, I can put 104 bricks on top of each other, so that the height is 100/104 cm. For the weight, I put together all my standard bricks (I have 440 of them), and went to the grocery to weigh them. Result is 2.44 lb, or 1.1 Kg. Dividing 1100 grams by 440 bricks gives 2.5 g per brick.