A simple trick for helping select the right button for your project: Find a scrap of your fabric and cut small slits in it that are about the length of the buttonhole you want to use. Space them approximately the distance apart that they will be on your garment. Take this with you to the button store. Slide any buttons you are considering (while still on the card) through the slit. It is much easier to imagine how they will look this way than just holding them near the fabric. This way you don't have to wait until you have completed the buttonholes and take the whole garment with you to the store. You also may decide on a different size button so you don't want to do the buttonholes first anyway.