The silver caps are considered part of the bead when measuring bead length. So the bead length is measured from the tip of the silver cap, across the Tulsi and to the tip of the opposite silver cap, like the below image illustrated. The image is zoomed in for ease of viewing. It is not life-sized. Each bead can be approx 4.75-6mm

There can be variances from necklace to necklace in the exact sizes of the Tulsi beads. The size of the silver caps and the amount of silver in the necklace determines the size classification of the necklace more than the size of the Tulsi itself.