Bead sizes explained: millimeters, inches, and what they look like
Nearly all beads are sized in millimeters, and if you grew up on inches, those numbers don’t mean much until you see them. Here’s the short version we give customers at the counter: 4mm is a peppercorn, 6mm is a pencil eraser, 8mm is a pea, 10mm is a chickpea, and 12mm is a thumbnail-width marble. A US dime is 17.91 mm across, so even an “enormous” 16mm focal bead is smaller than a dime.
Bead size conversion chart (mm to inches)
| Size (mm) | Inches (decimal) | Inches (approx. fraction) | Beads per inch |
|---|---|---|---|
| 2 mm | 0.079″ | ~5/64″ | 12.7 |
| 3 mm | 0.118″ | ~1/8″ | 8.5 |
| 4 mm | 0.157″ | ~5/32″ | 6.4 |
| 5 mm | 0.197″ | ~3/16″ | 5.1 |
| 6 mm | 0.236″ | ~1/4″ (scant) | 4.2 |
| 7 mm | 0.276″ | ~9/32″ | 3.6 |
| 8 mm | 0.315″ | ~5/16″ | 3.2 |
| 10 mm | 0.394″ | ~3/8″ (generous) | 2.5 |
| 12 mm | 0.472″ | ~15/32″ | 2.1 |
| 14 mm | 0.551″ | ~9/16″ | 1.8 |
| 16 mm | 0.630″ | ~5/8″ | 1.6 |
| 18 mm | 0.709″ | ~23/32″ | 1.4 |
| 20 mm | 0.787″ | ~25/32″ | 1.3 |
How bead size is actually measured
Bead size is the diameter — the straight-line distance across the bead — not the circumference, and not the hole. Measure with calipers across the widest point, perpendicular to the hole. The hole (drill) size is listed separately and matters for choosing your stringing wire or cord.
Shaped beads get two numbers. A rondelle is measured width × height, so an “8×5mm rondelle” is 8mm across and 5mm along the hole — it strings like a 5mm bead in length but looks like an 8mm from the front. Bicones and cubes are usually measured point to point or edge to edge along the hole. Natural stone beads routinely run 0.2–0.5mm over or under their stated size; that’s normal, and it’s why we round strand estimates.
Which bead size suits which project
- 2–4mm: seed-bead territory — spacers, delicate stacking bracelets, bead weaving, and filling gaps between larger beads.
- 6mm: the dainty all-rounder. Light on the wrist; a 7″ bracelet takes about 26 of them.
- 8mm: the most popular size we sell. Substantial without being heavy — the default for gemstone stretch bracelets and mala-style necklaces.
- 10–12mm: statement bracelets and chunky necklaces. Weight adds up fast with stone beads.
- 14mm and up: focal beads — usually one to three per piece, flanked by smaller beads.
How many beads for a bracelet or necklace?
Take the finished length, subtract roughly half an inch for the clasp and findings, convert to millimeters, and divide by the bead size. A 7″ bracelet with a 0.5″ clasp leaves 6.5″ (165mm) of beading — that’s 20 beads at 8mm, or 16 at 10mm. For a stretch bracelet with no clasp, skip the allowance. The calculator above does the arithmetic and also estimates how many 15–16″ strands to buy — buy a spare strand for anything precise, since bead sizes vary.
Chain sizes explained: what the millimeters mean
A chain’s size is its width — how wide the chain looks lying flat, measured in millimeters across the links. It is not the length and not the link size. The quick mental anchors: a 1mm chain is paperclip-wire thin, 2mm is pencil-lead width, 3.5mm is a phone-cable width, and 6mm is as wide as a drinking straw. Coin comparisons work too, but use the coin’s edge: a 2mm chain is about as wide as a nickel is thick (1.95mm).
Which chain width should you choose?
- 1–1.5mm: delicate. Best for pendants under ~10mm and layering; fine chains are also the easiest to break, so avoid them for heavy charms.
- 2–3mm: the everyday sweet spot — visible but not loud, strong enough for most pendants. Our most-sold range.
- 4–6mm: the chain becomes the jewelry. Worn alone or as the anchor piece in a stack.
- 8mm and up: statement chains — check weight before committing to a long length; a wide chain in a heavy metal wears very differently at 24″ than at 18″.
Chain length guide
| Length | Name | Where it sits (average adult) |
|---|---|---|
| 14–16″ | Choker | Snug at the base of the neck |
| 18″ | Princess | On the collarbone — the most common pendant length |
| 20–24″ | Matinee | Between the collarbone and the bust |
| 28–36″ | Opera | On or below the bust; can be doubled |
Lengths are for necklaces; standard bracelets run 7–8″ and anklets 9–10″.
How to measure a chain you already own
Lay the chain flat and measure straight across it at its widest point with a ruler or calipers — that’s the width in millimeters. For length, measure end to end including the clasp. If you’re matching a chain to a pendant, the pendant’s bail (the loop it hangs from) must fit over the chain and its clasp.
Frequently asked questions
How big is 8mm?
8mm is 0.315 inches — just under 5/16 of an inch. It’s about the size of a small pea, slightly larger than a standard pencil eraser (6.5mm), and less than half the width of a US dime (17.91mm). On a ruler, it’s a bit less than a third of an inch.
Is 6mm or 8mm bigger?
8mm is bigger than 6mm — 2mm larger in diameter, which is about a third bigger across and roughly twice the volume. On the wrist the difference is obvious: 6mm reads as dainty, 8mm as substantial.
How many 8mm beads fit a 7-inch bracelet?
About 20. A 7-inch bracelet with a half-inch clasp allowance leaves 6.5 inches (165mm) for beads, and 165 ÷ 8 = 20 beads. For a stretch bracelet with no clasp, about 22.
How do I measure a bead?
Measure the diameter — straight across the widest point, perpendicular to the hole — with calipers or a bead gauge. Without calipers, line up 10 beads snugly on a ruler and divide the total length by 10; that averages out small variations.
What is 8mm in inches?
8mm equals 0.315 inches, or just under 5/16 of an inch. To convert any millimeter size to inches, divide by 25.4.
What does a 3mm chain mean?
A 3mm chain is 3 millimeters wide across the links — about the width of a phone charging cable, or four credit cards stacked flat. Chain size describes width, not length; length is listed separately in inches.
What is the most common necklace chain length?
18 inches, called princess length. It sits on the collarbone and is the standard length for wearing a pendant. Chokers run 14–16 inches, and longer matinee styles run 20–24 inches.
