Converting women's shoe sizes into men's shoe sizes varies by country and also by manufacturer. South Korea is an exception, as they do not offer separate sizing systems for men, women, girls, or boys; instead, they measure in millimeters. Women's and men's equivalent shoe sizes alternate between having the men's sizes and the women's sizes indicated by larger numbers; this varies by country. You can find your shoe size in any country's system by measuring your feet and having those measurements handy when you shop.
Remove your shoe from the opposite foot to your dominant hand. Wear whatever socks or stockings you intend to wear with the shoes you are considering. Trace the foot on the paper. Your feet are usually slightly different sizes, and most of the time, the foot opposite your non-dominant hand is the largest.
Measure the tracing from the furthest points at either end. Write the measurement in millimeters, centimeters, and inches and label them clearly.
Consult conversion charts, such as I18guy's International Shoe Size Conversion Chart or Gempler's Shoe Size Conversion Chart. Using the measurements taken from tracing your foot, you can narrow down the size of shoes most likely to fit you. No matter what sizing system is used, all sizing systems are based on basic measurements.