This is a Barbie-like doll that I own. It is 12 inches tall. That makes the Lilliputians half the size of a Barbie doll.
Isaac Asimov annotated the 1980 edition of Gulliver's Travels, and made the following comment about the 6" people Swift created:
As it turns out, everything on the island is on the scale of one to twelve; that is, the island's inches are equilivant to our feet. Since the Lilliputian whom Gulliver first sees is very nearly six inches high, we can assume that Gulliver is very nearly six feet tall...
However, 1/12 is not the true measure of the size of the Lilliputians. They are 1/12 as tall as we are, but also 1/12 as wide and 1/12 as thick. The total volume of one of them, and therefore the total weight, is 1/12 x 1/12 x 1/12, or 1/1,728 of ourselves.