All measurements below are in CM and these are measurements of the finished coat, not your body.
To help determine your measurements, take a padded coat you have that fits well, close the zippers, then lay it flat. Take the measurements from seamline to seamline or end point to end point, and compare them with the chart below. This should provide you with a good reference. Note that the puffiness or thickness of your padded coat may affect how loose or tight the coat feels on you.