How Do I Choose the Right Thread Weight for Sewing?

The right thread weight depends on your project. For most sewing, quilting, and embroidery, a medium weight thread — 40 or 50 weight — is the best starting point. Fine weight thread (60 to 100) works well for detailed work like micro quilting or small lettering. Heavy weight thread (3 to 12) is best for decorative stitching and big-stitch hand quilting. As a general rule, the higher the thread weight number, the thinner the thread.

When it comes to sewing, thread is an essential component that can literally make or break your project. Here are five key things to know about thread weight.

1. What Does the Fraction on a Spool Mean?

The top number tells you the weight of the thread and the bottom number tells you how many plies — or strands — are twisted together.

For example: 50/2 means 50 weight and 2 plies.

2. How Thread Weight Works

The higher the thread weight number, the thinner the thread. A 12-weight thread is actually heavier than a 50-weight thread because it is denser. It would take 12 kilometers of 12-weight thread to equal 1 kilogram, compared to 50 kilometers of 50-weight thread to reach the same weight.

3. Weight Categories at a Glance

• Medium Weight — 40 or 50
  The most common weight range for everyday sewing.
• Fine Weight — 60 to 100
  A thinner thread that blends into fabric and is ideal for detailed work.
• Heavy Weight — 3 to 12
  A thick, bold thread used for decorative and hand stitching.

4. Most Common Uses by Weight

• Medium weight (40 or 50): Serging, machine embroidery, piecing, and quilting.
• Fine weight (60 to 100): Micro quilting, small lettering on machine embroidery, English paper piecing, and stitch in the ditch.
• Heavy weight (3 to 12): Big-stitch hand quilting, decorative stitching, and crocheting.

5. What About Your Bobbin?

For most sewing, it's ideal to have the same weight thread on top as in the bobbin. Test it out and see what works best for your machine and project.

Machine embroidery works a little differently. For freestanding lace, you want matching thread on both sides. For standard embroidery, you actually want the bobbin thread to pull to the back — so if you're running 40 weight on top, a 60 or 90 weight in the bobbin is ideal.

Who knew there'd be a science behind the thread itself! The most important thing is to use good quality thread and match it to the right project. When in doubt, start in the middle — a 50 weight is a reliable choice for almost everything.

Have Questions About Thread?

We carry a carefully selected range of threads for quilting, embroidery, and bobbin work. If you're not sure which thread is right for your next project, we're happy to help.

Shop Thread Kits →

📧 info@mygirlfriendsquiltshoppe.com
📞 435-213-3229

Frequently Asked Questions

What do the numbers on a thread spool mean?
The first number is the thread weight and the second number is the ply — how many strands are twisted together. A spool labeled 50/2 is 50 weight thread made of 2 plies.

Is a higher or lower thread weight number thicker?
A lower number means thicker thread. A 12-weight thread is much heavier and more visible than a 50-weight thread.

What thread weight is best for quilting?
40 or 50 weight thread is the most common choice for quilting. 50 weight is ideal for piecing and general quilting, while 40 weight adds a bit more definition and works well for machine embroidery.

What thread weight should I use for machine embroidery?
40 weight is the standard for machine embroidery. For the bobbin, a 60 or 90 weight thread helps the bobbin thread pull to the back, which gives you a cleaner finish on the front of your design.

What is fine weight thread used for?
Fine weight thread — 60 to 100 weight — is best for detailed work like micro quilting, small lettering in machine embroidery, English paper piecing, and stitch in the ditch.

What is heavy weight thread used for?
Heavy weight thread — 3 to 12 weight — is used for big-stitch hand quilting, decorative stitching, and crocheting. It creates bold, visible stitches that are meant to be seen.

P.S. Not sure where to start? A 50 weight thread is the most versatile option in any sewing room — it handles piecing, quilting, and general sewing with ease. Once you've got that covered, a 40 weight for embroidery and a fine weight for your bobbin will have you set for almost any project. Shop our thread collection →