Typical bra sizing is super confusing, and that goes double for younger girls who are looking for a soft top and barely have any boobs to begin with. We’ve simplified the situation by sizing using a single measurement.
TO MEASURE YOURSELF FOR AN OOMBRA, all you need to do is take a soft tape measure and wrap it around the biggest part of your chest - usually this is the nipple line, which means the part of your chest including your nipples. Make sure the measure is wrapped straight around you, without dipping far down your back or riding high up towards your neck. If you like tighter-fitting garments, pull the tape measure so that it is snug; if you like everything loose, measure with the tape a little loose as well. Your measurement is the number of inches in circumference.
Each OOMBRA size covers a 2" span. If you are right on the cusp between sizes - let’s say you measure 30" exactly - then choose to go with the bigger or smaller size based upon whether you like your garments to fit looser or tighter on top.
ONE BIG SIDE NOTE ABOUT OUR SIZING: if your boobs are bigger than a B cup in traditional bra sizing, then the difference between your chest circumference and your ribcage circumference is greater than 2". We have designed our bigger sized OOBRAs to accommodate for bigger boobs, but some girls have much smaller ribcage measurements than chest measurements. If this describes you and if you are right in between sizes, we recommend sizing down so that the elastic along the bottom fits nicely at your ribcage.