Honestly, you can't really determine that based on your weight and height. Also, it's going to vary depending on the brand (you can be a different size depending on the store).
What I would suggest: Most online stores have a "size chart". Take your measurements (bust, waist, hip, etc.) and compare them to the size charts of some US online clothing stores. If you're actually looking to purchase an item from a US store, then use their size chart in particular.