What length in pixels does a Wings3D unit of measurement equate to?

[dawntreader]

I have printed a measurement block on my Makerbot Replicator 2 printer.
I made a series of blocks stacked on one another from 50WU (Wings Units) down to 5WU reducing in increments of 5WU
| 05|____
| 10.......|____
| 15..............|____
| 20.....................|____
| 25............................|____
| 30...................................|____
| 35..........................................|____
| 40.................................................|____
| 45........................................................|____
| 50________________________________________|

Then I got a ruler and measured each line of the printed lines on the block and got the following
05WU = 05mm
10WU = 10mm
15WU = 15mm
20WU = 20mm
25WU = 25mm
30WU = 30mm
35WU = 35mm
40WU = 40mm
45WU = 45mm
50WU = 50mm
Therefore 1WU = 1mm when exporting to a .stl file that is to be printed on a Makerbot Replicator 2 3d Printer.

Hope this helps