The Ultimate Bead & Thread Size Reference Guide

Seed beads, natural stones, bone, and glass bead strands—Delica, cylin, and more! (A Complete Guide!)

Understanding bead sizing can be quite perplexing, as different materials employ various sizing systems, and many of these systems overlap yet convey different meanings. This guide meticulously breaks down each major bead category, clarifying how sizing operates for each type while providing clear charts for reliable reference.

This Page Is Designed to Be a reference. Copy the information, keep the info, come back to it.

This guide is:

• Material-specific
• Clearly segmented
• Neutral and educational
• Useful to beginners and professionals

·       It answers the questions:

·  Why do bead sizes measured in millimeters never feel exact in real life?

·  Why do beads with the same listed size look different once strung together?

·  What matters more for bead sizing: diameter, thickness, or hole size?

·  Why does bead weight affect how many beads I get more than bead size does?

·  Why do natural beads (stone, bone, glass) vary in size even when machine cut?

·  Why does changing bead material change how big a bead looks, even at the same size?

·  Why do bead size charts never match exactly between suppliers?

·  How much size variation is considered normal and acceptable in beads?

·  Why do some beads feel heavier or bulkier than others of the same size?

·  Why does my finished jewelry change length when I swap bead sizes or materials?

1. Understanding Bead Sizing Systems (Start Here)

There are two main sizing languages used in beadwork:

A) Seed Bead “Aught” Sizes (/0)

Used for:

• Czech seed beads
• Miyuki seed beads
• Most small glass seed beads

Rule to remember:

The higher the number, the smaller the bead

B) Millimeter (mm) Sizes

Used for:

• Natural stone beads
• Bone beads
• Glass bead strands
• Wood, shell, crystal

Rule to remember:

mm size = bead diameter measured straight across

These two systems do not convert perfectly.

2. Czech Seed Beads (Size 2/0 – 11/0)

Sizing, Characteristics & 22 g Vial Counts

Czech seed beads are one of the oldest and most widely used seed beads in the world. They are known for their rounded shape, traditional manufacturing process, and slightly organic variation, which gives finished beadwork a softer, more textured appearance than precision-cut Japanese beads.

They are especially popular for:

·       Traditional and Indigenous-style beadwork

·       Loom work

·       Embroidery and appliqué

·       Cultural, heritage, and organic designs

Unlike Japanese seed beads, Czech seed beads are not perfectly uniform by design — this variation is often preferred for patterns that value texture and character.

How Czech Seed Bead Sizes Work

Czech seed beads use the aught (/0) sizing system.

Important rule:

The larger the number before /0, the smaller the bead

Example:

2/0 = very large seed bead

11/0 = small seed bead

Sizes represent relative ranges, not exact measurements.

Czech Seed Bead Size Conversion & 22 g Vial Counts

The table below shows:

Approximate bead diameter

Typical visual/functional characteristics

Estimated bead count per 22 g vial

⚠️ Counts are approximate and vary by finish, hole size, and manufacturer.

What Makes Czech Seed Beads Different

Czech seed beads are intentionally less uniform than Japanese seed beads.

This results in:

·       Slight size variation from bead to bead

• More variation in hole diameter
• A softer, more organic finished look
• These traits make them ideal for:
• Freeform designs
• Traditional patterns
• Bead embroidery where texture adds depth

Important Notes on Czech Seed Beads

• Slight size variation is normal and expected
• Hole sizes vary more than Japanese seed beads
• Bead counts are estimates, not guarantees
• Excellent choice for organic, textured, and heritage designs

3. Miyuki Seed Bead Sizes (6/0 – 15/0)

Miyuki seed beads are known for:

• High uniformity
• Consistent hole size
• Precision beadwork (peyote, brick stitch)

Miyuki Seed Bead Size Chart

📌 Why Miyuki beads are referenced so often

• Reliable sizing
• Predictable patterns
• Ideal for advanced techniques

4. Natural Stone Bead Sizes (2 mm – 25 mm)

Natural stone beads are measured only in millimeters.

They are:

• Machine cut or hand polished
• Naturally variable
• Sized by diameter, not hole size

·       Beads per Strand (15–16 Inch Strand Reference)

Natural Stone Bead Size Chart

📌 Stone bead notes

• Expect ±0.3–0.7 mm variation
• Heavier stones may feel larger
• Hole sizes vary independently

5. Bone Bead Sizes & Characteristics

Bone beads are usually:

• Hand carved or polished
• Slightly irregular
• Measured in mm, but often approximate

Common bone bead types:

• Rounds
• Discs
• Spacers
• Carved shapes

Typical Bone Bead Size Ranges

📌 Bone bead notes

• Thickness matters as much as diameter
• Hole placement may vary
• Sizing is always approximate

6. Glass Bead Strands (Non-Seed Beads)

Glass bead strands include:

• Lampwork beads
• Pressed glass
• Fire-polished beads

These are sized in millimeters, not /0.

Common Glass Bead Strand Sizes

📌 Glass bead notes

• Shape affects perceived size
• Hole size varies by style
• Strands often range 14–20 inches (count will be in descritions)

7. Common Sizing Mistakes (And How to Avoid Them)

❌ Assuming seed bead sizes convert exactly to mm
❌ Expecting natural beads to be perfectly uniform
❌ Ignoring thickness on bone and glass beads
❌ Confusing bead diameter with hole size

Best practice:
Always check diameter, hole size, and material together.

8. Delica Beads & Cylin Beads (Precision Beadwork Explained)

Delica beads and cylin beads are not the same as traditional round seed beads, even when they share the same /0 size.

They are:

• Precisely cut
• Uniform in height and diameter
• Designed to stack perfectly with no gaps

This makes them the preferred bead for loom work, peyote, brick stitch, and advanced bead weaving.

What Makes Delica & Cylin Beads Different

9. Delica & Cylin Bead Size Chart

Although they use the same /0 numbering system, Delica and cylin beads are slightly larger than round seed beads of the same size because of their straight sides.

Delica / Cylin Bead Size Reference

📌 Important note
An 11/0 Delica is NOT the same size as an 11/0 round seed bead. Patterns are written specifically for one or the other.

10. Thread & String Selection (This Is Where Most People Get Stuck)

Choosing the wrong string causes:

• Broken thread
• Poor tension
• Misshapen beadwork
• Frustration

FireLine Thread Compatibility Guide

(We carry 4 lb, 6 lb, 8 lb)

FireLine is a braided, fused thread known for strength and abrasion resistance.

FireLine by Bead Type

📌 FireLine is not elastic and is ideal for bead weaving and loom work.

 Nymo Thread Compatibility

(we carry Size D and Size 00)

Nymo is a traditional nylon beading thread, flexible and widely used in classic beadwork.

Nymo Thread Guide

📌 Nymo benefits from:

• Thread conditioning
• Gentle tension control

Silk Thread Compatibility

(You carry Size D–FFF)

Silk thread is used primarily for knotting, especially with stone and glass beads.

Silk Thread Guide

📌 Silk stretches slightly — pre-stretch before knotting.

 Elastic Cord Compatibility

(we carry 0.8 mm & 1.0 mm)

Elastic is used primarily for bracelets and slip-on designs.

Elastic Size Guide

📌 Always ensure:

• Bead hole is larger than cord diameter
• Use secure knots or adhesive

11. Bead Size → String Quick Reference Table

(This is the table people screenshot and keep)

Final Best Practices

• Match bead type to thread type
• Do not substitute Delicas for round seed beads
• Always test fit before committing
• Natural materials vary — plan accordingly