In this post you will learn how to understand thread sizes.
If you’ve ever stared at a spool of thread and wondered what all those numbers mean, you’re not alone. Thread sizes in sewing can be confusing—thread weight, tex sizes, denier, commercial thread sizes… what?! But don’t worry. Once you get the basics, it’s actually pretty easy to choose the correct thread size for every project.
So whether you’re working with cotton thread on lightweight dresses, polyester thread for everyday clothes, or bonded nylon thread for heavy-duty upholstery, this guide will help you figure out the best option.
Let’s break it down in simple terms.
Why Thread Size Matters So Much
Choosing the right thread isn’t just about color—it’s about durability, tension, and how your project looks when finished.
- Too thick = bulky seams and possible puckering.
- Too thin = weak seams that snap under pressure.
- Wrong thread tension = skipped stitches or uneven seams.
The goal? Match your thread weight to the fabric weight so everything lays smooth and lasts long.
Thread Sizing Systems (Explained Simply)
There are a few different ways to measure thread sizes in sewing, depending on the brand and country. Here’s the no-nonsense version:
1. Weight (wt)
This is the most common for home sewing. The lower the number, the thicker the thread.
- 30 wt = thicker (good for topstitching).
- 40 wt = standard all-purpose thread.
- 60 wt = fine thread for delicate fabrics.
2. Tex Sizes (tex)
Tex measures how many grams 1,000 meters of thread weigh.
- Tex 25–35 = everyday sewing.
- Tex 70–90 = heavy-duty stuff (like upholstery or canvas).
- Tex 135+ = serious industrial projects.
A quick cheat: smaller tex = thinner thread.
3. Denier (d or den)
Denier is grams per 9,000 meters. It’s used more for polyester thread and industrial threads. Higher denier = thicker thread.
Example: 225 den ≈ 40 wt ≈ Tex 25.
4. Commercial Thread Sizes
If you’re buying bonded nylon thread or bonded polyester thread, you’ll see commercial sizes like 46, 69, or 92. These are just denier divided by 10.
- Size 69 = Tex 70–90 (upholstery, leather, marine use).
- Size 92 = Tex 90–100 (heavy canvas, gear bags).
Thread Sizing Conversion Chart (Weight, Tex, Denier & Ticket Number)
| Common US Measurement | Tex Size (tex system) | Thread’s Denier (denier count) | Ticket Number | Weight of a Thread (wt) | Recommended Needle Size | Use |
|---|---|---|---|---|---|---|
| 60 wt (thin threads) | Tex 15–20 | ~135 den | Ticket 120 | Smaller weight number | 60/8 – 70/10 | Delicate fabrics, lightweight fabrics, embroidery |
| 40 wt (general rule) | Tex 25–35 | ~225 den | Ticket 80–100 | Lower number = thicker | 75/11 – 90/14 | Everyday sewing projects |
| 30 wt (heavier threads) | Tex 35–40 | ~300 den | Ticket 60–80 | Increased diameter of the thread | 90/14 – 100/16 | Topstitching, heavier materials |
| 20 wt (heavy threads) | Tex 70–90 | ~600 den | Ticket 30–50 | Heavy-duty threads | 100/16 – 120/19 | Heavyweight fabric, upholstery |
| 15 wt (marine grade thread) | Tex 135+ | ~1200 den | Ticket 20–30 | Heavy duty / bonded nylon thread | 120/19+ | Outdoor, marine projects |
Keep Your Threads Organized!
Once you know which thread sizes to use, keeping them organized will save you time and money. Check out my guide on how to organize sewing threads like a pro and make your sewing projects easier than ever.
Organize Your ThreadsThread Types & Their Best Uses
)
Cotton Thread
Soft, breathable, and perfect for delicate fabrics and quilting.
- Best size: 40 wt (Tex 25–30) for sewing, 60 wt for super fine seams.
Polyester Thread
Strong, slightly stretchy, and fade-resistant. Great for clothes, home decor, and anything that needs a bit of give.
- Best size: Tex 25–35 for general sewing, Tex 70–90 for heavy projects.
Bonded Nylon Thread
If you’re sewing leather, canvas, or upholstery, this is your friend. Coated for strength and abrasion resistance.
- Best size: Size 69 (Tex 70–90) for upholstery, Size 92 or higher for marine gear.
Bonded Polyester Thread
Similar to nylon but better for outdoor projects because it resists UV rays. Perfect for boat covers, outdoor cushions, and marine grade thread projects.
Silk Thread
Beautiful, smooth, and ideal for fine garments and embroidery projects. Usually very thin, around 50–60 wt.
Level Up Your Sewing Skills!
Want to master thread choices even more? Check out my detailed guide on 7 Neutral Thread Colors Perfect for Every Fabric. It’s packed with expert tips to help you match thread colors flawlessly for all your sewing projects.
Read the GuideMatching Thread to Fabric
Here’s a quick cheat sheet to avoid guesswork:
| Fabric Type | Thread Type & Size |
|---|---|
| Lightweight fabrics (voile, silk) | Cotton thread or fine polyester thread, 50–60 wt (Tex 15–25) |
| Everyday clothes (cotton, blends) | Polyester thread, 40 wt (Tex 25–35) |
| Decorative & embroidery | Polyester embroidery thread, 40 wt (120d/2) |
| Heavy fabrics (denim, canvas) | Polyester or bonded nylon thread, Tex 40–70 |
| Upholstery & leather | Bonded nylon thread or bonded polyester thread, Size 69–92 |
| Outdoor & marine projects | Marine grade thread (bonded polyester, Size 92+) |
Types of Thread
| Types of Thread | Features | Best Use |
|---|---|---|
| Cotton Thread | Soft, breathable, pairs with natural fibers | Quilting, delicate fabrics |
| Polyester Thread | Slight stretch, durable, a popular choice for clothes | General sewing projects |
| Bonded Nylon Thread | High tensile strength, smooth finish, often used in descriptions of nylon fabrics | Upholstery, leather, heavier materials |
| Marine Grade Thread (Bonded Polyester) | UV resistant, good choice for outdoor use | Boats, cushions, marine grade thread |
| Silk Thread | Fine, smooth, available in vibrant colors | Couture, embroidery projects |
How to Choose the Right Thread Size (Quick Steps)
- Look at the thickness of the thread: A lower number or smaller numbers in weight mean a thicker thread.
- Check fabric type: Lightweight fabrics = thin threads, heavyweight fabric = heavy duty or heavy threads.
- Check fiber content: Natural fibers (cotton, silk) pair best with cotton thread or silk thread. Synthetic fabrics need polyester thread or bonded nylon thread.
- Use conversion charts: A good sewing thread size chart or nylon thread sizes chart helps compare different thread weights and different systems.
- Adjust your stitch: The stitch length and stitch density should match the size of thread and size needle.
- Replace your needle: Always use a new needle when switching to heavy-duty threads for heavier materials or heavier threads.
Needle Size vs Thread Size
Don’t forget your needle! The needle size should match the thread weight. Too small, and the thread shreds; too big, and you’ll get skipped stitches.
- 40 wt / Tex 25–35 = 75/11 to 90/14 needle
- 30 wt / Tex 40 = 90/14 needle
- Tex 70+ = 100/16 to 120/19 needle
A good rule: The needle eye should be about 40% larger than the thread.
Master Needle Sizes Too!
Understanding thread sizing is just the beginning. Learn how to choose the correct needle size for every fabric in my full guide. Plus, grab a free PDF cheat sheet to make sewing easier!
Get the Free PDFTips for Perfect Stitches
- Adjust thread tension when you switch to thicker or thinner threads.
- Use longer stitch length for thicker threads (3–4 mm).
- Always test on a scrap piece first.
- Keep different thread weights in your sewing kit—switching makes a huge difference in professional-looking results.
Quick Sewing Thread FAQ
Final Thoughts
Understanding thread sizes in sewing doesn’t have to be overwhelming. Once you get the hang of thread weight, tex sizes, and the difference between bonded nylon thread, cotton thread, and polyester thread, you’ll be able to pick the correct thread size for any project—whether it’s a lightweight dress or a heavy-duty outdoor cover.
So next time you’re shopping for thread, check the label for thread weight, tex sizes, or commercial thread sizes, and you’ll always pick the right one. Happy sewing!
Want to dive deeper? Check out the official Gutermann Thread Guide for professional insights on thread sizing and fabric matching.
In this post you have learned how to understand thread sizes.
This post has affiliate links * Affiliate Link. This means that if you click on the link and purchase an item, I will receive a small percentage of your purchase (at no extra cost to you)
