Sewing Knits: 9 Common Mistakes and How to Fix Them

In this post, you’ll learn how to sew knits with confidence, avoid beginner mistakes, and get professional-looking results on every project.

If you’ve ever tried sewing with knits, you probably know the struggle: wavy seams, hems that don’t stretch, or stitches that mysteriously skip no matter how carefully you sew. Knits are some of the most comfortable fabrics to wear, but for beginners, they can feel like sewing’s final boss battle.

Here’s the truth though—knits aren’t scary once you know a few tricks. In fact, many sewists end up loving them more than woven fabrics because knits don’t fray, they’re comfy, and they give garments that modern, easy-to-wear fit.

In this guide, I’ll walk you through the most common mistakes people make when sewing knits—and, more importantly, how to fix them. By the end, you’ll have the confidence to tackle T-shirts, leggings, or even that cozy sweater dress you’ve been eyeing.

If you’re new to sewing knits, start with my first post, How to Sew Knit Fabrics Like a Pro — it covers all the basics, from the best tools and stitches to choosing the right fabric. Once you’ve read that, come back here to learn how to avoid the most common mistakes beginners make when sewing knits and how to fix them like a pro.

Ready to put these tips into practice? Check out my guide to sewing with knit fabrics, including 14 easy beginner projects you can start today.

Why Do Knits Intimidate Beginners?

Most beginners start with woven fabrics like cotton or linen. These are stable, don’t move around much, and you can usually sew them with a straight stitch and be done with it. Knits, on the other hand, are stretchy and bouncy. That stretch is amazing when you wear the garment—but it means your stitches need to stretch, too.

The good news? Once you learn the right tools and techniques, knits are actually faster to sew than wovens. No fraying edges, no complicated finishing—just cut, sew, and wear.

9 Common Knit Sewing Mistakes

Mistake 1: Using the Wrong Needle & Thread When Sewing Knits

The 1 knit frustration: skipped stitches and tiny holes. Nine times out of ten, this happens because of the wrong needle.

The Fix:

• Use a ballpoint or stretch needle. These glide between knit fibers instead of breaking them.
• Choose the right size:
  • Lightweight jersey → 70/10
  • Medium-weight → 80/12
  • Heavy ponte/fleece → 90/14

And don’t forget about thread:

• Polyester thread is perfect for knits because it has a little stretch.
• Avoid 100% cotton thread—it breaks easily.
• For maximum stretch, load woolly nylon into your bobbin or serger loopers.

 Pro Tip: Swap your needle before every knit project. A fresh needle solves a world of problems.

Want to see the exact tools I reach for when pattern drafting, upcycling, and fine-tuning fit? Check out my guide, Best Sewing, Pattern Drafting & Upcycling Tools I Use . It pairs perfectly with your knit-sewing toolkit—think rulers and French curves, rotary cutters, pattern weights, tracing paper, markers, and more—so you can upgrade your setup and your results.

Mistake 2: Ignoring Fabric Stretch Direction When Sewing Knit Fabric

Cutting without checking fabric stretch is a recipe for disaster. If you cut leggings with the stretch running up and down instead of side-to-side… let’s just say they won’t be wearable.

The Fix:

• Gently pull your fabric before cutting to find the direction of greatest stretch.
• Match fabric stretch to your pattern’s requirements (some need 50% or more).

Types of Knit Fabrics

Not all knits are created equal. Each one behaves differently, so choosing the right type matters.

Knit Fabric Type	Stretch %	Weight	Best For	Notes
Single Jersey	30–50%	Light–medium	T-shirts, dresses	Curls at edges
Rib Knit	50–100%	Medium	Cuffs, neckbands	Very stretchy
Interlock	30–40%	Medium–heavy	Skirts, structured tops	Stable, doesn’t curl
French Terry	20–40%	Medium	Hoodies, joggers	Loops on one side
Ponte	20–30%	Heavy	Dresses, pants	Stable, less stretch
Lycra/Spandex Blends	50–100%	Varies	Leggings, activewear	Needs special handling

 Beginner Tip: Start with cotton jersey or interlock. Save slippery rayon or Lycra for later.

Mistake 3: Why Elastic Stitches Are Essential When Sewing Knit Fabric

Knits stretch. That’s their magic—and also their biggest challenge. If you sew them with a regular straight stitch, your seams will almost certainly snap the first time you wear the garment. That’s why elastic stitches are a must when working with knits.

The Fix:

• Choose the Right Stitch

Stitch Type	When to Use	Notes
Zigzag stitch	All-purpose seams, hems	Beginner-friendly, flexible, easy to adjust width/length
Stretch stitch	Seams	Looks like a straight stitch but stretches beautifully; great for activewear
Overlock/Serger	Seams + finishing	Strong, stretchy, professional—but not required
Twin needle	Hems, cuffs, necklines	Store-bought look: two lines on top, zigzag underneath for stretch

 Pro Tips:

• Start with a narrow zigzag if you’re new to knits.
• Lower presser foot pressure on lightweight fabrics to prevent stretching.
• Use polyester thread (cotton breaks easily) and try woolly nylon in the bobbin or serger for extra stretch.
• Always test your stitch on a scrap of your fabric before sewing your actual garment.
•  Think of elastic stitches as the insurance policy for your knit projects: they keep your seams flexible, durable, and looking professional—even after lots of wear.

Watch: How to Sew Stretchy Knit Fabric – Step-by-Step Video

Sometimes seeing the technique in action makes everything click! In this video, I’ll show you exactly how to sew stretchy knit fabrics using simple stitches on a regular sewing machine. You’ll learn how to avoid wavy seams, skipped stitches, and popped threads — perfect for beginners who want smooth, flexible results.

Mistake 4: Not Adjusting Stitch Settings for Sewing Knits

A straight stitch may look neat, but it’ll snap the moment you stretch the fabric.

The Fix:

Use stretch-friendly stitches:

• Narrow zigzag → simple, effective.
• Stretch stitch → looks straight, but stretches.
• Serger/overlocker → professional finish, not essential.
• Twin needle → gives hems a store-bought look. 

Step-by-Step: Sewing Knit Seams

• Pin or clip pieces (right sides together).

• Machine settings: Zigzag 2.5–3 mm width, 2–3 mm length. Lower foot pressure for lightweight knits.

• Sew slowly, guide fabric without pulling.

• Trim seams if needed; finish with zigzag or serger.

• Press gently, never stretch while pressing.

Troubleshooting

• Seams wavy → Lower foot pressure or use walking foot.
• Skipped stitches → Check needle type and thread.  Quick Checklist   Mistake Cause Fix Holes in seams Wrong needle Use ballpoint/stretch needle Skipped stitches Wrong thread/needle Polyester thread + stretch needle Wavy seams Feed issues Walking foot, reduce foot pressure Curled edges Fabric type Use clips, rotary cutter Puckered hems Too-tight stitches Twin needle, lengthen stitch

Advanced Tips

• Use stay tape on necklines and hems.
• Clip curves to prevent bunching.
• Always test on scraps first.
• Mix pins + clips for tricky areas.
• Use woolly nylon for super stretch.

Choosing the Right Twin Needle

Needle type: Stretch or ballpoint twin needle. 

Size:

• Lightweight knits: 2.5 mm (70/10)
• Medium knits: 3.0 mm (80/12)
• Heavy/stretch fabrics: 3.5–4.0 mm (90/14)

Tip: Twin needles come with single shank, compatible with most domestic machines.

Threading the Machine 

• Place two spools of thread on the spool pins.
• If your machine only has one pin, use a second spool holder or wind thread onto a bobbin and use it as your second spool.

•  Take both threads and thread them together through the upper thread guide and tension discs, just as you normally would with one thread.
• When you reach the final thread guides (usually above the needle bar), separate the two threads.

• Thread the left needle with one spool of thread.
• Thread the right needle with the second spool.
• Make sure the threads are not twisted or crossing.

• Insert the bobbin thread just like you normally would.
• The bobbin will form a zigzag on the underside that allows stretch.

Pro Tip: Use polyester threads for strength and elasticity.

How to Sew with a Twin Needle on Knits

A twin needle is one of the best-kept secrets for sewing knits. It creates two clean, parallel lines on the right side of your garment and a zigzag on the underside, giving your hems stretch and a professional finish. Perfect for T-shirts, leggings, and knit dresses!

Here’s exactly how to sew with it:

• Prep Your Hem
• Fold the hem allowance to the wrong side of the fabric.
• Press with steam to create a crisp fold.
• Secure with clips, pins, or fusible hem tape if your knit is slippery.

• Choose Your Settings
• Stitch type: Straight stitch (the twin needle automatically forms zigzag underneath).
• Stitch length: 2.5–3 mm.
• Presser foot:
• Use a zigzag/all-purpose foot (wide enough for both needles).
• Tension: Start at default; adjust if you see puckering.

• Sew from the Right Side
• Place your hem under the presser foot with the folded edge toward the right.
• Important: Sew with the right side of the fabric facing up.
• This way, the neat parallel lines show on top.
• The zigzag bobbin thread on the underside secures the raw edge.
• Sew slowly and evenly—don’t pull or stretch the fabric.

• Finish the Hem
• Don’t backstitch (it can tangle with a twin needle). Instead:
• Leave long thread tails.
• Pull them to the wrong side with a hand needle and knot off.
• Press the hem gently to set the stitches.

Troubleshooting Twin Needle Sewing

• Skipped stitches → Use a stretch/ballpoint twin needle.
• Puckering fabric → Lengthen stitch slightly or lower top tension.
• Tunneling (ridge between lines) → Loosen tension or use fusible hem tape for stability.
• Threads snapping → Make sure they’re not twisted in the guides.
• Broken needle → Use the zigzag foot (not straight-stitch foot) and check your stitch plate width.

Pro Tip: Always test on a scrap of your knit fabric before hemming. Each knit behaves differently, so a quick test saves your project!

Mistake 5: Skipping Proper Pressing When Sewing Knit Fabric

Pressing is the secret to pro-looking knits. If you skip it, seams can look wavy or develop a cracked look.

The Fix:

• Press seams flat first to set stitches.
• Then press seam allowances open or to one side.
• This “underpressing” helps fabric recover from stretching and keeps seams crisp.
• Use low heat + press cloth. Steam lightly, but never stretch fabric while pressing.

Mistake 6: Stretching Fabric While Sewing Knits (and How to Stop It)

It’s tempting to tug fabric through your machine, but that creates lettuce-like seams.

The Fix:

• Let feed dogs guide fabric—don’t pull.
• Use a walking foot if your machine struggles.
• Lower foot pressure for lightweight knits.

Mistake 7: Skipping Stabilizers and Finishing Steps When Sewing Knit Fabric

Knits don’t fray, but stabilizers are still essential for professional results.

The Fix:

• Add clear elastic to shoulder seams.
• Use stay tape on necklines.
• Press hems, then finish with a twin needle or coverstitch.

Learn exactly how to use a stabilizer, spray starch, and wash-away tape— plus quick DIY options to make your own at home—in my full guide: How to Use a Stabilizer, Spray Starch or Wash-Away Tape (Save Time & Money) .

Mistake 8: Choosing the Wrong Sewing Pattern for Knit Fabric

Not all patterns are knit-friendly. Using a woven pattern without adjusting leads to saggy results.

The Fix:

• Choose patterns labeled “for knits.”
• Learn negative ease: knits are often drafted smaller so they stretch to fit.
• Start with simple knit patterns like tees or leggings.

Mistake 9: Skipping Practice and Patience When Learning to Sew Knits

Knits reward patience. Jumping straight into a tricky Lycra dress will leave you frustrated.

The Fix:

• Test stitches on scraps first.
• Begin with simple projects (infinity scarf, knit skirt, basic tee).
• Build skills step by step.

Essential Tools for Sewing Knits for Beginners

• Ballpoint/stretch needles
• Walking foot
• Clips (great for slippery knits)
• Twin needle

Pinning vs Clipping Knit Fabric – What’s Best for Beginners?

• Pins: Use fine, short ones perpendicular to seam line. Great for stable knits.
• Clips: Best for slippery or stretchy knits, won’t leave holes.
• Mix both: Pins for corners, clips for curves or hems.

Sewing Knits for Beginners – Quick FAQ & Troubleshooting

Still have questions about sewing knits for beginners? Here are quick answers to the most common problems sewists face

Do I need a serger?

No! Zigzag or stretch stitches on a regular machine work fine.

Why are my seams wavy?

Usually you’re pulling the fabric or there’s too much presser foot pressure. Try a walking foot.

What thread is best?

Polyester. Cotton tends to break on knits.

How do I stop curling edges?

Use clips and a rotary cutter to control the roll as you cut and sew.

Sewing Knits for Beginners – Final Tips for Confident, Stretchy Seams

Sewing knits doesn’t have to be stressful. Yes, they stretch, curl, and sometimes misbehave—but once you avoid these common mistakes, you’ll see how forgiving they actually are.

Start small, practice often, and remember: every project builds your skills. Before long, you’ll be whipping up T-shirts, leggings, and sweaters with confidence.

 Ready to dive in? Grab some cotton jersey, pop in a ballpoint needle, and start sewing—your future self (and your wardrobe) will thank you.

In my next tutorial, I’ll show you how to sew with knit fabric step-by-step and create a cozy, flattering dress you’ll love wearing all season long.

In this post, you have learned how to sew knit fabric the right way—plus the common mistakes to avoid for smooth, stretchy seams every time.