The problems with the metric system are largely the problems of using base-10 arithmetic. Say you are a carpenter; your boss hands you a meter stick and asks you to cut him a piece of wood 1/3 meter long.<p>Well, there's no line on the stick for that. You go back to the boss, and say this meter stick isn't accurate enough; Its only marked to centimeters. So he grumbles, buys you one which is marked to millimeters, and you try again....still no line on the meter stick for 1/3rd of a meter...<p>Wiki has a beautiful chart relating the olde-tymie english units like inches, barleycorns, and furlongs. These units were developed ad-hoc by people living in every kind of society from industrial stretching back to the paleolithic. And yet, they are remarkably coherent--once you notice it. What is striking is how often the factors of 2 and 3 are involved in converting one unit into another; e.g., three barleycorns is an inch, 6 picas is an inch, 3 feet is a yard, etc.<p>Metric <i>calculations</i> are ostensibly easier because we use base-10. If we used, say, base-6 or base-12, metric calculations would be as difficult to do in our heads as the English units are. But all those ancient English units would super-easy, because its super-easy to multiply or divide by 2 or 3 in base-6 or base-12.<p>You can see this most clearly, ironically, in nations like, say, Japan, who have adopted the metric system the most throughly. There, they never use decimeters, or even centimeters. Every measurement is given in millimeters, and you tend to find lengths like 24 and 48 millimeters to be especially previlent--because they both have lots of factors of 2 and 3, making it easy to divide lengths into the most common ratios which are actually used.<p>Its why eggs are sold by the dozen and beer comes in 6-packs.