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Trimming Corners


Trimming is when you cut the seam allowances smaller or on an angle to reduce bulk. You’ll need to trim to turn the piece right side out, if the seam allowances stop the piece from fully turning.

Trimmed seam allowance

Trimmed seam allowance

Trimmed corner

Trimmed corner

Notched curve

Notched curve


Trim anytime you are asked to trim the seam allowance in the pattern instructions. Trim inner and outer curves, and trim seam allowances on enclosed seams such as collars, tabs, pocket flaps and fabric belts. Corners must be trimmed to reduce lumps inside the point of the corner. Trim seam allowances on facings (page link) so the garment edge lies flat.

Tips + Notes

  • Trim with pinking shears to quickly reduce bulk and finish the seams at the same time.
  • Trimmed too close? If so, go back to the machine and resew the seam a couple of millimeters away from the original seam line, only in the area where you trimmed too far. Use a short stitch length. If you snipped too close to the seam line, you could also apply a small piece of fusible interfacing (page link) to reinforce the area and ensure it doesn’t fray through the stitching line.


With corners, you want to remove as much as bulk as possible. All of the seam allowance needs to fit inside the point of that corner.

Trimming Corners (1)

Trim diagonally across the corner first. Snip right across both sides of the seam. Get close to the point of the corner. Leave only about 1mm–2mm of space above the stitching.

Trimming Corners (2)

Trim two more diagonal cuts with the scissors at a sharper angle toward the corner. Turn the corner right side out, and if there is too much bulk inside the corner point, turn it back inside out and make another angled cut on each side of the point.

Trimming Seam Allowances


Generally seam allowances start at 5⁄8″ (1.5cm), and I trim them to ¼” (6mm). You can also aim to trim your seam allowances in half, which is easy to eyeball without having to use a tape measure. To reduce bulk even more, trim both seam allowances in half and then trim one of them in half again, so it’s half the width of the other. This creates a smoother transition and reduces the chance of seeing the outline of the seam allowances on the right side of the garment.

Grading Seam Allowances


This is one thing I never quite got the hang of in high school sewing class! If you angle the scissors, tilting the blades toward you as you trim, you’ll end up cutting one side of the seam allowance shorter than the other with a single cut. Grading takes practice, and the difference between the two sides is subtle. It ensures that there aren’t two thick seam allowances with blunt edges sitting right on top of each other. The more you angle your scissors, the greater the variance between the two layers. Grading is faster than trimming the two layers individually, but it creates less of an obvious difference.

Clipping Inner Curves


For inner curves, clip into the seam allowance, stopping about 1⁄8″ (3mm) before the stitching line. Make your snips about ½” (1.3cm) apart or closer together in very curved areas. The snips release the seam allowance so the piece can be turned and pressed flat. Clipping the seam allowance makes it easier to do. If you turn the piece and it won’t turn fully, turn it back inside out and make more snips.

Notching Outer Curves


For outer curves, cut pie-shaped notches from the seam allowance, stopping about 1⁄8″ (3mm) before the stitching line. Place these notches about ½” (1.3cm) apart from each other at the top edge. Make more notches around very curved edges. When the piece is turned right side out, the space between the notches closes as the seam allowance comes together. Without these pie-shaped notches, you would see lumps where the seam allowance bunches up inside the seam. If you turn the piece and there are lumps where the seam allowance overlaps, turn it back inside out and cut more notches.

Tips + Notes

  • Don’t trim a seam that needs to be matched to another seam, because your trimmed seam will come up short. If you must, make sure the seam line is marked so you know where to line up the pieces.
  • Clip and notch curves at different points on the top and bottom seam allowances so they don’t pull in the same spots. Doing so takes time, and it’s more important for thicker fabrics and less important for thinner ones because bulk isn’t as much of an issue.
  • After trimming, understitch (page link) facings (page link) to help them roll to the inside and create crisp edges.

Source : The Sewtionary An A to Z Guide to 101 Sewing Techniques + Definitions
About the Author : Tasia ST. Germaine