I'm from the US, and so am comfortable with the imperial system....but the math is indisputably easier in the metric system. The only part I have difficulty with in the metric system is when I have to estimate a size that would be bigger than three inches, and smaller than half a meter. The foot and inch come in handy in these instances because they seem more "human" estimates. For instance 25 decimeters....I have a hard time guessing it...but as I said, I grew up using the imperial system. Also, what happens when you need something smaller than a millimeter? I don't know the unit. I wish they had taught us more in school about it.