I am always size S in tops and bras, and this one is a way too uncomfortable fit. I can not send it back because I have removed the tags before trying I thought it would be a perfect fit. Even if you follow the size guide it did not work for me, so Myprotein should fix the sizing issue.

Gorgeous sports bra, really beautiful fit and the back is amazing. I ordered a S and it first perfectly. I was a bit worried reading the reviews that said order a size up, but if you have a small chest like me it fits perfect in your normal size.

Very supportive and looks fab. I use this for running and hiit especially because it is high impact. 

Looked a beautiful top online but sizing is ridiculous! Order minimum 1-2 sizes up but at that, very thin across chest 

This is an amazing sports bra, and although all the comments are right, it does come up small, it's super comfy and flattering when on, offering enough support for small chest. I'm a fairly flat chested curvy pear shape, so this is perfect for that kind of body type. I measure 30inches (a/b cup) around my rib cage and got a Large (if that helps).