Most people should realize they can ask Google to "convert 5cm to inches" and a widget will show up with the answer. You can convert all sorts of strange units that way without having to exercise your brain too much.
To the extent many Americans don't like the metric system, most of the rest of the world especially dislikes the inches and gallons, because the different units of distance or volume or whatever don't go in powers of 10. It's 12 or 4 or 1760. That is an incredibly cumbersome system to do science in. Fortunately a yard is close to a meter, and an inch is about the distance of the last joint on your thumb.
(Spanish vocabulary here: pulgada = inch; pulgar = thumb.)
People here in Mexico use metric and American units for different things. For example, you would normally buy a gallon of paint, but your gasoline comes in liters). Metric is clearly preferred, but there's still enough American commercial influence here that most people can convert.
