If I recall correctly, it's a little above my belly button.
Also, there's a way to measure on the site to figure out what size would be best for you. I went with a small and it fits good, but all in all, it depends on your personal measurements.

This is from the underworks website on how to measure:
"1. How to measure: First take a snug measurement under the bust line with a tape measure. Next take another measurement over
the fullest part of your chest. Again not too tight but not too loose. Take the average of theses two measurements and apply the result to the scale provided below. Each item has a different scale based on the elasticity of the fabric used and the cut of the garment, so please pay attention to the sizing scale for each style."