Your frame size measured as measured by the width of your elbow or wrist is correlated to your bone mass and muscle mass. Women generally have a smaller frame size then men for any given height.
Quick Measurment Method
The simplest way to measure your frame size is to wrap your thumb and your pointer finger around the smallest part of your wrist. If your fingers don't touch, it means that you have a large frame. If your fingers are just touching that means you have a medium size frame If your fingers overlap that means you have a small frame. This method of measuring your frame size is not as accurate as the elbow measurment method and should only be used as an approximation.
Elbow Measurment Method
A more accurate way of measuring frame size is to measure your elbow breadth against your height. To measure your elbow breadth, bend your forearm up at a 90 degree angle, with your hand open, turn your palm so that it's facing your body. Next take your pointer finger and your thumb of your other hand and place them on opposite sides of your elbow at the elbow joint. Then measure the distance between your fingers with a ruler.
The following is data from Metropolitan Life on the medium frame sizes of men and women. If you are below the medium you have a small frame size, if you are above the medium you have a large frame size.
Men (Medium Frame Size)
Women (Medium Frame Size)