The metric system is not based on the arbitrary construct of the human body; rather, on precise and definite standards.
Metric system uses base 10, just like our number system, so it is much easier to learn, remember and convert between units.
The prefixes used in the metric system are from Latin and Greek, and they refer to the numbers that the terms represent. (For example, "kilo" as in "kilogram" means 1 000 and "milli" means 1/1000). You can now easily calculate the number of millimeters in a kilometer. (how many inches in a mile?)
Metric system are interrelated in such a way that one unit is derived from other units without conversion factors. E.g. 1N (Newton) is the force needed to give 1kg(kilogram) of mass an acceleration of 1ms2 Try that with the 'English' units.
The metric system is used in most places around the world, so our use of it allows scientists from disparate regions to use a single standard in communicating scientific data without vocabulary confusion.
