So...what if you don't have a tape measure...but you do have some fairly new bras? How can you use them to determine your band size?
Put one of those puppies on upside down, cups over belly. Like so:
Now, how much space is between you and the band?
If the fit is loose, the bra band is too large and you should go down to the next one. If you can fit a whole hand width between you and the band, you might need to go down more than one band size. If the fit is uncomfortably snug--like my Elila is to me currently--you will need to go up in the band. If the band is comfortable, it will stay the same but you may need to adjust for cup size.
You can also check for snugness by checking how much tension is on the upper and lower hooks of the bra. If they're straining, go a little larger so that you don't warp the shape of the cup in front.
So...if it's comfortable, flip the bra right side up and swoop and scoop. That will determine the next step in your journey. Bon voyage!!