The "Subtract 10" rule is indeed unreliable, particularly in larger sizes, since the sizing systems are using different units of measurement (Centimeters and Inches). To convert to US measurements, double to get the circumference in centimeters and divide by 2.54 to convert centimeters to inches. So a European 48 corresponds to a US 37.8, or approximately a US 38. A European 58 corresponds to a US 45.7, or approximately a US 46.
3/13/14 at 3:26pm