My brain does the same thing, and I always measured in metric in school! But I actually have no idea of my weight in kgs or height in cms, as most of my life I've heard those things in lbs and feet/inches, despite being in Canada. I also don't know my cooking measurements in ml (might be because everything I use from cook books is in tsp tbsp cups).

Google has a great function for this. Just open a google search window, type in the amount you have, and it comes up with the equivalent in the most likely form. Ex. if I typed in "84 inches" it gives me an "84 inches = 2.1336 meters". Click the more about calculator and it shows you how to do other conversion options too.