How to Do a Swayback Adjustment

Do you get a pool of excess fabric bunching at your lower back? Learn how to do a swayback adjustment with this simple pattern fix.

Do you find you have bunched-up fabric pooling in your lower back on your me-made garments? You’re far from alone—it’s one of the most common fit issues out there. This excess fabric usually happens when your back is particularly curved or when your back length is shorter than the pattern assumes. Either way, a swayback adjustment will sort it out.

A quick note: this adjustment works best on patterns with a center back seam, as it creates a curve that nestles into the small of your back. If your pattern doesn’t have a center back seam and you want the best-fitting result, consider adding one—just add a seam allowance and cut two pieces rather than one on the fold.

How to Tell If You Need a Swayback Adjustment

• There’s loose, excess fabric pooling at your lower back
• Important: If the garment is tight over your bum and riding up (which is pushing fabric into your lower back), that’s a different issue—you may need to grade up at the hip or do a full bum adjustment instead

Measuring How Much to Adjust By

Try on your muslin and pin out the excess fabric in a wedge shape, with the largest amount pinched at the center back, tapering out to nothing at the side seams (forming a diamond shape). This one’s tricky to do by yourself—you’ll likely need to pinch the fabric, check in the mirror, take the garment off and safety pin it, try it on again, and repeat until you’ve got it right.

Once you’re happy, measure how much fabric you pinched out at the center back—that’s the amount you need to remove from your pattern.

On Patterns Without a Waist Seam

Step 1: Draw a line across the back bodice pattern piece at waist level (Line 1). Mark the seam allowance at each end of this line.

Step 2: Mark the distance you need to remove at the center back seam, centering it around Line 1 so that half the distance is above and half is below the line. Draw lines connecting those marks to Line 1 at the side seam allowance (Lines 2 and 3).

Step 3: Cut along Line 2 from the center back, ending at the side seam allowance. Snip into the seam allowance from the other side to create a small hinge. Swing the bottom piece up so that Line 2 meets Line 3.

Step 4: Trace your pattern piece, smoothing out the new curve at the center back.

On Patterns With a Waist Seam

Step 1: Draw the seam allowance around the bottom edges of the back bodice pattern piece. Draw a horizontal line (Line 1) across the waistline, from the corner of the seam allowances at the center back to the side seam.

Step 2: Make a mark above Line 1 on the center back seam—this mark should be the amount you need to remove (the distance you pinched on your muslin). Draw a line connecting this mark to Line 1 at the side seam allowance (Line 2).

Step 3: Cut along Line 1, starting at the center back and ending at the side seam allowance. Snip into the seam allowance from the other side to create a hinge. Swing the bottom piece up until it meets Line 2.

Step 4: Trace your pattern piece, following the original hemline of the piece you swung up. If your pattern has darts, redraw the dart legs so they’re straight.

Note: If the excess fabric on your muslin was equally distributed above and below the waist seam, you can also adjust the skirt piece in a mirror image of what you did for the bodice—removing half the fabric above the waist and half below.

You Did It!

No more fabric pooling at your lower back! Your garment will now follow the curve of your body beautifully.

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.