Im trying to make an enclosure for a single sa 12 but the only wood they sell out here is 18 mm thick mdf, I'm wondering how to compensate this into my cut sizes for the box I wanna build I wanna do 15 h x 17d x 22w with the port being 2" wide and tuned to 32 hertz any suggestions?

You are not going to notice 0.050"

If you are that concerned about it make all your cuts in mm.

Did they say it was 18mm? Normally it is 19mm ( = to 3/4"). When I lived in Korea and Germany, it was always 19mm... Either way I wouldn't sweat it, your cut errors will more than likely be greater than 1mm...

I also would do it in metric as mentioned. Just round up a mm to get an even #... A tad bigger won't hurt anything, it may actually help!

Thanks for the advice I just don't wanna end up with gaps in my box if you kno wit I mean

Just do the conversions and acount for your wood thickness. If you were going to go 15" x 17" x 22" internal you would make the front/back 41.6cm x 56cm, the top/bottom 43cm x 56cm and the ends 41.6cm x 46.6cm... Just do the conversions and account for the 1.8cm MDF thickness.

If you are worried about gaps, maybe you should pay to have the box built...