Summary

Testing accuracy of your X and Y in a good manner.

Instructions

If you just built your 3d printer, use this to test how accurate your belts are adjusted. Measure with a digital caliper!

Remember that the first layer always usually is difficult to measure accurate. The numerous mistakes i made trying to do that!

So just sit and wait until you see a wall getting built which is exactly 2 mm thick and at the outside it should measure 100.00 x 100.00 millimeter. If not, then consider whether you need to readjust your belt or maybe you're over or underextruding?

Or in case of slic3r maybe just the width of your settings aren't matching your nozzle (as it doesn't do that automatically ok)?

100x100 mm test