Estimate then calculate the width of a quarter in imperial units.
As an ESTIMATE a quarter is about 1 inch wide (imperial) 1 inch is 25.4 mm (metric)
First of all, I do understand the advantages of the metric system. It has a standardized convention for naming units. It works in base 10 for simple manipulation and use with decimals. It was designed to fit with certain properties of the physical world (a gram of water is a milliliter of water, at normal temperature and pressure, for example).