Very simple 100x100x100 object. I print the tower separately to give the option of excluding the object if needed if you only want to print X and Y.
The corners are rounded on X and Y so that if you don't have pressure advance calibrated or enabled, it won't mess with your dimensions.
Wait about 20 minutes for everything to cool down to room temp before measuring to get accurate results.
Math: 100 * (current esteps) / (what you got in mm)
What number you get is your new esteps value.