If one of your measurements is between two sizes, order the smaller size for a tighter fit or the larger size for a more relaxed fit. Alternatively, you can measure a top or pant you currently wear comfortably and use that to compare to the sizing charts.
Increase your South African/UK shoe size by 3 to determine your US size for shoes. For example, if you are a size 4 shoe, then you would be a size 7 in our Zone Anywear shoe. Easy peasy.