The exact length of 1 LDU
Originating in the LDraw community, the LDU has become the standard measurement in the wider LEGO community. In this unit, the spacing between the centres of two adjacent LEGO studs is exactly 20 LDU. The metric system estimates an LDU to be 0.4mm, and the imperial system indicates it is 1/64". But which is correct? This article, written in a scientific manner and published at a Swedish university as a joke - but with real findings - proves that an LDU is 0.4mm.