Things You'll Need
Instructions
Break all of the stitching along both armhole seams on each side of the shirt with a seam ripper. The armhole seams are the stitched lines that go around the top of the shoulder and under the arm. The armhole seams join the top part of the sleeves to the shoulders of the shirt fabric.
Measure the length that you want to reduce from the sleeves. Add 5/8 inch to this measurement for seam allowance, and write down the total length on a piece of paper. Seam allowances are 5/8 inch on all seam lines for this project.
Trim the length that you wrote down in Step 2 off of the top edges of the sleeves to reduce the length of the sleeves. The top edges of the sleeves are the sections of the sleeves that were stitched to the armhole seams on the opposite side of the sleeve from the cuff.
Fold under 5/8 inch of the outer fabric on the top edge of the sleeves. The outer fabric is the top side of the fabric which is visible when you wear the shirt right side out. Fold under 5/8 inch of the outer fabric on the armholes (where your arms go through the shirt into the sleeves.) These 5/8-inch folds are your seam allowances.
Lay the seam allowances against each other on the underside of the sleeve and the armhole. The underside is the side of the fabric that is not visible when you wear the shirt right side out.
Position one hand underneath the fabric. Put a pushpin in this hand. Push the pin up through the fold line of the seam allowances and then push the pin back down through the fold line. Repeat until you have pinned the seam allowances together completely. Machine-stitch along the pinned lines.
Measure the length you want to reduce from the hemline along the bottom of your flannel shirt. Increase this measurement by 1 inch and write down the total length on the piece of paper. Trim this length off the bottom edge of your flannel shirt to reduce the length of the shirt. Measure 1/2 inch up from where you just cut and fold the edge of the fabric under. Fold the fabric under another 1/2 inch and stitch the folds down.
Turn the shirt inside out. Put the shirt on. Insert pushpins through the material parallel to the existing side seam lines to take the side seams in and mark where you would like the new side seam lines to sit if you want the shirt to fit more snugly around your waist. The side seam lines are the seam lines that go from the bottom of the armhole seams under the arms to the hemline at the bottom of the shirt. If you decide to take these lines in, the shirt will fit more tightly.
Machine-stitch down the pinned side seam lines. Trim off the leftover fabric at the original seam lines.