Hi Waldemar, I never measure just a single cell, but measure a number of cells perpendicular to the parallel walls. I measure from the outside edge of the first cell wall to the inside edge of the last cell wall. Then I divide that measurement by the number of cells. These results are multiplied by 10 so that they are consistent with other cell measurements based on the length of 10 cells which is common in the cell size discussions concerning small cell beekeeping. Now, how I do it and how it should be done is probably another question :>)) Regards Dennis -- Visit www.honeybeeworld.com/bee-l for rules, FAQ and other info ---