How to Do a Narrow or Broad Back Adjustment

Is your garment too loose or too tight across your upper back? Learn how to do a narrow or broad back adjustment with this simple pattern fix.

If your garment fits well at the front but something’s off at the back—either straining across your shoulder blades or drooping with excess fabric—you likely need a back width adjustment. It might be tempting to just make a different size for the back and front, but that’s not a great idea because the seams won’t match up and you’re unlikely to get a good fit. A wide or narrow back adjustment is much more effective, and it’s not hard!

How to Tell If You Need a Broad Back Adjustment

• The back feels tight, but the front fits fine
• The fabric is straining at the back armscye
• The armscyes are being pulled toward the center of your back

How to Tell If You Need a Narrow Back Adjustment

• There’s excess fabric at the back—either around the armscyes or in vertical folds down your back
• It looks loose and droopy at the back but fits well at the front
• The armscyes are sticking too far out from your body at the back

Measuring How Much to Adjust By

For a broad back: On your muslin, make a vertical slash down each side of the back. Measure how much the slash needs to spread open for you to feel comfortable and no longer find the back tight. This is tricky to do yourself, so alternatively you can add 1/2 – 1″ (1.2-2.5 cm), make a new muslin, and assess whether you need more.

For a narrow back: On your muslin, use safety pins to pin out vertical folds of fabric in two lines down your shoulder blades until it feels the right width. Measure how much fabric you pinched out in one of the folds.

Making a Broad Back Adjustment: Less than 3/4″ (1.9 cm) adjustment.

If you have a small adjustment to make, this approach means no extra dart is required.

Step 1: On the back bodice pattern piece, mark the seam allowances around the side seam, armscye, and shoulder. Draw a vertical line down from the shoulder, and then at a right angle over to the side seam, below the armscye. Draw a second line at a right angle from the vertical line over to the armscye, at the height where you need the most additional width added.

Step 2: Cut down the vertical line from the shoulder, turning at the bottom and cutting until the seam allowance of the side seam. Snip into the seam allowance on the other side (from the side seam) to form a hinge. Cut along the short line, starting at the inner end and going to the seam allowance of the armscye. Again, snip into the seam allowance on the other side.

Step 3: Spread your pieces apart so that the width you need to add to the pattern piece (half of the total width you need to add across the full back) is where the red shaded box is. To achieve this, you will gently swing out the pieces, keeping the hinges intact. At the shoulder, where you cut through, you can either create a new hinge by taping it at the seam allowance and re-cutting in, leaving a little hinge, or you can just make sure the stitching lines are still touching as you spread the pieces apart. Note that there is a limit to how much you can spread the pieces without breaking the hinges or distorting the pattern pieces – if you need more room, follow the alternative method below.

Step 4: Trace the piece, smoothing out the shoulder and armscye shapes.

Note: The armscye length hasn’t changed, so there’s no need to adjust your sleeve.

Making a Broad Back Adjustment: More than 3/4″ (1.9 cm) adjustment.

Step 1: On the back bodice pattern piece, draw a vertical line from the middle of the shoulder down to just below underarm level. Then continue the line diagonally over to the side seam, roughly 2″ (5 cm) below the underarm.

Step 2: Cut along this line to separate the piece into two. Spread the smaller piece away from the main piece until the vertical gap equals the width you need to add, keeping the lower edges aligned.

Step 3: Trace your pattern piece, evening out the side seam (this will add a bit of extra width there too).

Step 4: The back shoulder is now wider than the front shoulder. You have two options: either adjust the front shoulder to match, or add a small dart at the back shoulder that’s the width of the gap you opened up (about 2″/5 cm long). The dart keeps the shoulders even while preserving the added width across your upper back where you need it.

Note: The armscye shape hasn’t changed, so there’s no need to adjust your sleeve.

Making a Narrow Back Adjustment: Less than 3/4″ (1.9 cm) adjustment.

If you have a small adjustment to make, this approach means the shoulder length is not affected, reducing the number of other adjustments required.

Step 1: On the back bodice pattern piece, mark the seam allowances around the side seam, armscye, and shoulder. Draw a vertical line down from the shoulder, and then at a right angle over to the side seam, below the armscye. Draw a second line at a right angle from the vertical line over to the armscye, at the height where you need the most additional width removed.

Step 2: Cut down the vertical line from the shoulder, turning at the bottom and cutting until the seam allowance of the side seam. Snip into the seam allowance on the other side (from the side seam) to form a hinge. Cut along the short line, starting at the inner end and going to the seam allowance of the armscye. Again, snip into the seam allowance on the other side.

Step 3: Overlap your pieces apart so that the width you need to remove from the pattern piece (half of the total width you need to remove across the full back) is where the red shaded box is. To achieve this, you will gently swing in the pieces, keeping the hinges intact. They will overlap at parts. At the shoulder, where you cut through, you can either create a new hinge by taping it at the seam allowance and re-cutting in, leaving a little hinge, or you can just make sure the stitching lines are still touching as you overlap the pieces. Note that there is a limit to how much you can overlap the pieces without breaking the hinges or distorting the pattern pieces – if you need more room, follow the alternative method below.

Step 4: Trace the piece, smoothing out the shoulder and armscye shapes.

Note: The armscye length hasn’t changed, so there’s no need to adjust your sleeve.

Making a Narrow Back Adjustment: More than 3/4″ (1.9 cm) adjustment

Step 1: On the back bodice pattern piece, draw a vertical line from the middle of the shoulder down to just below underarm level. Then continue the line diagonally over to the side seam, roughly 2″ (5 cm) below the underarm—this is Line 1. Draw a second vertical line parallel to Line 1, spaced the distance you need to remove—this is Line 2.

Step 2: Cut along Line 1, separating the pattern piece into two. Slide the smaller piece to overlap the main piece until it meets Line 2, keeping the lower edges aligned.

Step 3: Trace your pattern piece, evening out the side seam.

Note: The back shoulder is now slightly narrower than the front shoulder. You can either adjust the front shoulder to be narrower too, or add a small dart or tuck to the front shoulder to even them out.

You Did It!

No more straining or drooping at the back! Your garment will now fit your back just as well as it fits your front.

Want to dive deeper into fitting? This adjustment and many more are covered in detail in Ahead of the Curve, our best-selling book on fitting for curves. And if you’d like in-depth video tutorials that go much deeper, check out Cashmerette Club‘s library of fitting masterclasses.