Beads Per Inch Chart by Bead Size in mm
The maths is one division: 25.4 ÷ diameter in millimetres, because an inch is exactly 25.4 mm. That is exact for round beads strung touching, which is how a plain strand sits on the thread.
| Bead size | Per inch | 7″ bracelet | 18″ necklace |
|---|---|---|---|
| 2 mm | 12.70 | 88 | 228 |
| 3 mm | 8.47 | 59 | 152 |
| 4 mm | 6.35 | 44 | 114 |
| 5 mm | 5.08 | 35 | 91 |
| 6 mm | 4.23 | 29 | 76 |
| 8 mm | 3.17 | 22 | 57 |
| 10 mm | 2.54 | 17 | 45 |
| 12 mm | 2.12 | 14 | 38 |
| 14 mm | 1.81 | 12 | 32 |
| 16 mm | 1.59 | 11 | 28 |
| 20 mm | 1.27 | 8 | 22 |
Seed Bead Sizes — and Why They Vary
Seed beads use the aught system: 11/0, 8/0, 6/0. The number originally described how many beads fitted in a given length, so a higher number means a smaller bead — the opposite of millimetre sizing.
Here is what most charts will not tell you: the aught system is a convention, not a standard. Every manufacturer applied it slightly differently, and they still do. Japanese brands are consistent with each other in the middle of the range; Czech beads and the very small sizes vary most.
| Size | ≈ mm | ≈ per inch | Note |
|---|---|---|---|
| 15/0 | 1.5 | 17 | Most variable size — Czech and Japanese differ noticeably |
| 11/0 | 2.1 | 12 | The default seed bead. Miyuki and Toho are close here |
| 11/0 Delica | 1.6 | 16 | A cylinder, not a round — narrower than a round 11/0 |
| 10/0 | 2.3 | 11 | Mostly Czech; less common in Japanese ranges |
| 8/0 | 3 | 8 | Consistent across Japanese brands |
| 6/0 | 4 | 6 | Often called E-beads |
These are nominal diameters, not specifications. For a large project, lay out one actual inch of your own beads and count — that is the only figure guaranteed to be right for the beads in your hand.
Working Out What to Buy
- Measure the finished length you want.
- Subtract the clasp — typically 0.5 to 1 inch.
- Multiply the remaining length by beads per inch.
- Add about 10%. Beads break, spacers eat length, and running out mid-strand with no matching dye lot is a genuine problem.
If you are alternating sizes, work out each separately. A pattern of one 8 mm bead and two 3 mm spacers repeats every 14 mm, so a 6.5-inch stringing length holds about 11 repeats — 11 large beads and 22 small — not something the simple per-inch figure will tell you.
Where the Simple Formula Stops Working
- Delicas and cylinder beads. They are not spheres, so they pack flush. Use the cylinder width, not a round-bead figure of the same aught size.
- Bicones and rondelles. The stringing dimension is the height along the hole, not the widest point. Measure the axis the thread passes through.
- Knotted strands. Pearl knotting adds roughly 1 to 2 mm between every bead, which over an 18-inch necklace removes several beads from the count.
- Memory wire and stiff cores. Beads sit slightly apart on a curve, so the effective count drops a little on tight radii.