i'm using inkscape to make files that i can cut on my laser printer, i know my kerf is .1mm so when i draw a box i make it 3.2mm square so that 3mm wood will fit, i just noticed that if i change the size of the stroke ( i've been using .3) then the dimensions of the box change , is there a setting to measure the actual size of the box and not depend on the size of the stroke? 

Preferences>Tools>Bounding Box>Geometric

thank you , i knew it must be a setting somewhere