The Best Threads for Bag Making (and How to Finally Understand Tex vs S!)

If you’ve ever stood in front of a wall of sewing threads, completely overwhelmed by all the numbers, weights, and labels — you are not alone!

When I first started bag making, I thought “thread is thread.” Oh, how wrong I was! Using the wrong type (or size) of thread can mean messy seams, broken stitches, or a domestic machine that sounds like it’s having a breakdown.

So today, let’s untangle the mystery. I’ll walk you through the different types of thread used in bag making, explain what all those confusing Tex and S numbers mean, and show you how to choose the right needle to match.

And if you’re more of a visual learner — don’t worry — you can download my free Bag Maker’s Thread Cheat Sheet at the end of this post to keep by your sewing table.

The Three Main Types of Thread for Bag Making

Standard Polyester Thread

• Usually labelled 120s or Tex 25–30.

• Fine, smooth, and perfect for light fabrics or linings.

• Works beautifully in domestic machines for small bags, cotton projects, or interior seams.

Think of this as your everyday, do-it-all thread — but not the one to rely on for heavy canvas or vinyl.

Bonded Polyester Thread

• Typically Tex 45 (60s) or Tex 70 (40s).

• Has a light coating (bonding) that strengthens it and stops fraying.

• Glides through thick layers, vinyl, and canvas like a dream.

This is my go-to for most bag projects. It gives a strong, smooth stitch line and can handle thicker materials without snapping.

Bonded Nylon Thread

• Heavy-duty and very strong.

• Often used in industrial machines for leather, outdoor gear, or upholstery.

• Has a tiny bit of stretch, so it’s not ideal for lightweight fabrics.

If you’re sewing heavy leather or multi-layered structured bags, this stuff is a powerhouse — but most domestic machines won’t love it.

The Difference Between the S System and the Tex System

This is the bit that confuses everyone, so let’s break it down simply.

The Ticket (S) System

Used mainly in the UK and Europe.

• Higher number = finer thread.

• Lower number = thicker thread.

Example:

• 120s = fine (for light fabrics)

• 60s = medium (great for most bags)

• 40s = heavy (for topstitching or leatherwork)

It’s based on length per gram: the more thread per gram, the finer it is.

The Tex System

Used internationally and by most industrial manufacturers.

• Higher number = thicker thread.

• Lower number = finer thread.

Tex measures the weight in grams of 1,000 metres of thread.

So:

• Tex 30 = fine

• Tex 45 = medium

• Tex 70 = heavy

🧵 Quick Comparison Guide:

Choosing the Right Needle

Always match your needle size to your thread thickness — it makes all the difference!

👉 Tip: If you hear your machine struggling, it’s probably a needle-thread mismatch.

Final Thoughts on the Best Thread for Bag Making

Once you understand Tex vs S, and how to match your thread and needle, everything in bag making feels a bit less chaotic. Your stitches get neater, your seams stronger, and your machine a lot happier.

You don’t need to memorise it all — just keep this handy:

👉 Download the Thread Cheat Sheet (PDF)

And if you’d like to see this in action, you can watch my full video here: Best Threads for Bag Making (and a Mystery Thread Unboxing

Until next time happy sewing and may your bobbin always be full Deb x