To convert binary to decimal in a binary coded decimal form, from 0 (0000) to 9 (1001) I used the double dabble method.

To find one of the fastest ways of certain logic I used the program Logisim.

The much smaller converter design are a lot smaller but do need about twice as long to convert the binary input in to a decimal output.

The download contains a world save, the Logisim project file and separate schematic files for both the stackable logic units, the first binary to decimal converter and the smaller 9 and 13 bit converters.