How important bead size is depends on the use of the beads. For stringing you would be most concerned with your desired length and need for precision between length and precise placement with various components within the string. For weaving you would be most concerned with the shape of the beads and how the different components fit with each other in order to achieve the final shape of the whole woven piece.
Guide to Bead Sizes Bead size is the distance between bead holes regardless of the overall shape of the bead. This length is the key measurement when combining beads on a length of cord, thread or wire, as it gives an overall length for a necklace or bracelet when the beads are hole to hole. The printable Bead Size Chart below shows standard sizing for both round and oval beads, and it can also be applied to cabochons. However, because monitors resolutions vary, to get a truly accurate representation of this Bead Size Guide you need to print it at 100% on a sheet of A4 paper (21cm by 29.7cm).