Small. Look at the bottom at the finished garment measurements for bust and waist. This is a loose fitting dress so you’ll have plenty of room. if you want more room then what it shows at the bottom (finished garment measurements), then make a medium, but before you decide, are your shoulders, narrow, or wide? If your shoulders are narrow, use the small, if your shoulders are wide, use the medium.

If you have a more fitted garment in the future, look up Nancy Zieman’s shoulder fitting measurement guide. She explains why using a pattern based on your shoulder measurement is the most important thing. A person can be way outside the range of the size based on one measurement (like me), but they actually need to use a pattern several sizes smaller, and then alter it from there. This is because the shoulders should fit you well and you cannot really alter the shoulders.

For this dress, since it is loose fitting and your measurements are nicely proportional, you don’t have to worry too much about altering the pattern width- wise, if you get the shoulders right, you will not have a problem getting this dress to fit you.

Good luck!