Why Your Shirt or Jacket Bunches in the Back

Sewing Solutions for a Smooth, Comfortable Fit at the Small of the Back

Have you ever slipped on a beautifully made shirt or jacket, only to find it bunching awkwardly in the small of your back or the middle of your back? It’s frustrating—especially when the front fits perfectly. Whether you're sewing your own clothes or adjusting store-bought garments, understanding why this happens is key to getting a smoother, more flattering fit.

Let’s break it down and explore how to fix it.

🔍 What's Causing the Bunching?

Excess Fabric at the Back Waist

The most common cause of bunching is extra fabric pooling at the lower back. This often happens if the back length is too long or if the pattern isn’t shaped enough through the torso. In sewing terms, the back isn’t contoured to your body’s natural curves.

Swayback Fit Issues

If your lower back curves inward more than average (a posture called swayback), standard sewing patterns may not lie flat against your back. The result? The fabric gathers at your waist, even if the rest of the garment fits fine.

Swayback is a common body variation, and fixing it is easier than you think.

Tight Shoulders or Upper Back

Sometimes the bunching lower down is caused by tightness up top. If your shoulders or upper back are restricted, the fabric has nowhere to go, so it ends up pulling and wrinkling below.

Posture Mismatches

Patterns are typically drafted for a “standard” posture. But what if you stand very straight or have a slightly rounded back? The result is often fabric tugging or gathering, especially along the back waist and spine.

🧵 How to Fix the Problem in Your Sewing Projects

If you're sewing your own garments, you're already ahead—you can tailor the fit before cutting your fabric. Here are some common adjustments:

✂️ Swayback Adjustment

The classic fix for back waist bunching.

Pinch out the excess fabric across the lower back in a horizontal tuck.

Measure and mark the amount you need to remove (typically ½" to 1").

Draw a horizontal wedge on your pattern’s back piece, tapering to nothing at the side seams.

This creates a gentle curve that hugs your back without restricting movement.

✂️ Shorten the Back Bodice

If the back length is too long overall—not just at the swayback—you may need a length adjustment.

Mark the pattern horizontally between the shoulder blades and the waist.

Fold out the excess evenly.

This is especially helpful on jackets and shirts with straight-cut backs.

✂️ Add Shaping With Darts or Seams

If your back needs more shaping, darts or princess seams are your best friend.

Add vertical darts on the back bodice to contour the fabric.

Or opt for princess seams if you want to design with more style flexibility.

✂️ Back Yoke for Better Fit

In shirts, a back yoke helps with shoulder fit and posture variation. It breaks up the fabric, so it lays smoother across the back and upper shoulders.

🧥 A Note About Ready-to-Wear Garments

If you're dealing with store-bought clothing, a tailor can often make simple fixes. Taking in the back seam, adding darts, or adjusting the shoulder slope can eliminate that bunching and make the garment feel custom-made.

But if you’re sewing your clothing? You’ve got all the control.

Always check the back fit in a mirror or photo before finishing your garment.

Make a muslin or toile if you’re unsure how a pattern will behave.

Use softer, drapier fabrics for shirts if your back has more curves—it helps them fall gracefully.

Back bunching isn’t a sewing mystery—it’s a clue. And once you understand it, you can turn that clue into a perfectly fitted top, shirt, or jacket that feels like it was made just for you, because it was.

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