The Metric System

The metric system confuses me. I don't understand it and spend too many minutes doing the conversion in my head. When we here heading back to Manilla from Bacquiao in the countryside, the highway sign said "450 km." After the sign, I started beginning the conversion in my head. 1 meter is three feet, there are 5280 ft in a mile, and there are 1000 meters in a km. By the time, i had finished the conversion there was another sign that said "420 km." I kinda gave up because my conversion was wrong. The gym, the highway, and the grocery store all use the international metric system. I hate it and reminds me of how much I love America.