How to Do a Full Bum Adjustment

Are your pants or skirt tight across your bum with draglines radiating to the side seams? Learn how to do a full bum adjustment with this simple pattern fix.

Got a full, fabulous bum? That’s something to celebrate! Unfortunately, many patterns don’t account for a curvier rear, which means you might need to make some adjustments. Much like it’s almost-namesake the full bust adjustment, the full bum adjustment also involves adding both length and width to give your body the space it deserves.

How to Tell If You Need a Full Bum Adjustment

• Your garment feels tight across your backside (and this tension might also make it feel snug across your stomach)
• You can see lines pulling outward from your bum toward the side seams
• The side seam wants to swing toward the back of your body
• Your back waistband is getting tugged downward and may be gaping open

Measuring How Much to Adjust By

For width: Unpick the side seams of your muslin from just under the waist down to your upper thigh. Let the fabric relax and measure the gap that opens up—that’s how much extra room you need around your hips. Divide this number by 2 to get Measurement 1.

For length: Check how far the back waistband has dropped from where it should sit (nice and level all the way around). That distance is Measurement 2.

Full Bum Adjustment on Pants

Step 1: Draw your seam allowances around the edges of the back pattern piece. Draw the following lines:

1. Start at outer corner of waist, draw line down to dart point (or around 1/3 of way down crotch curve if no dart) then across to crotch.
2. Through the middle of the dart (if no dart, from where line 1 bends up to the waist)
3. From the knee, diagonally up to meet line 1 (exactly angle doesn’t matter)
4. Vertical line through lowest point of crotch curve to inside leg

Step 2: Cut along line 1, starting at the crotch, going across and up to the top corner. Stop when you hit the seam allowance, then snip in from the other side to make a hinge.

Cut down line 2, stopping just shy of line 1 to create another hinge.

Pivot the upper section upward to open a horizontal gap with parallel edges (shown in green) —this gap should equal half of measurement 2. You’ll notice the dart area spreading apart vertically as you do this, and the upper crotch section will stick out beyond the lower section (this area is shown in red) —this overhang should match measurement 1.

Need more width? Snip through that dart hinge and slide things over until you’ve got enough.

Step 3: Cut along line 3 from the top down to the seam allowance, snipping in from the opposite side to create a hinge. Pivot this section until your crotch edges line up again.

Step 4: Cut along line 4 from the top down to the seam allowance, creating one more hinge. Pivot this piece to open a gap equal to half of measurement 2.

Step 5: Trace your adjusted pattern piece and redraw the dart with the original dart legs. If your pattern didn’t have a dart to begin with, add one now—make it the width of the gap that opened up, ending where line 2 finishes.

Full Bum Adjustment on a Skirt

Adjusting a skirt (or the skirt portion of a dress) follows a similar approach, just simplified.

Step 1: Work through steps 1 and 2 from the pants instructions above, but skip lines 3 and 4 entirely. When you open up your horizontal gap, make it the full amount of length you need (all of measurement 2, not half).

Step 2: Trace your new pattern piece, keeping a straight line down the center back. This adds width all the way down the skirt back, and will work whether or not your skirt has a center back seam.

If your skirt has a center back seam and you’d prefer the skirt to taper back in below your bum and maintain the original hem circumference, just ease the center back line into a gentle curve below that point.

You Did It!

No more tugging, pulling, or straining across your backside! Your garment will now fit your curves comfortably.

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.