Size of the seed bead is indicated by number, for example 9/o. The bigger the number, the smaller the bead. The table below presents the size markings of different beads, and their approximate diameter in mm.
| Size | Bead diameter ca. (mm) | Hole diameter ca. (mm) | pcs of beads/10g ca |
|---|---|---|---|
| 1/o | 6.6 | 2.0 | 40 |
| 2/o | 6.1 | 1.6 | 50 |
| 3/o | 5.6 | 1.3 | 55 |
| 4/o | 5.1 | 1.2 | 75 |
| 5/o | 4.6 | 1.1 | 120 |
| 6/o | 4.1 | 1.0 | 130 |
| 7/o | 3.5 | 0.9 | 210 |
| 8/o | 2.9 | 0.8 | 420 |
| 9/o | 2.6 | 0.8 | 680 |
| 10/o | 2.3 | 0.7 | 910 |
| 11/o | 2.1 | 0.6 | 1300 |
| 12/o | 1.9 | 0.5 | 1650 |
| 13/o | 1.7 | 0.4 | 2900 |
| 14/o | 1.6 | 0.4 | 3250 |
| 15/o | 1.5 | 0.4 | 6250 |