DIY Alterations Tutorial: Slimming + shortening blazer jacket sleeves with lining

I haven’t been posting as much due to work and prepping for exam cramming, but follow me on Twitter for some fitting room photos and more. I’ve fallen very behind on emails and comments but will try to respond to any questions soon. Thank you for your patience!

On to today’s post ~ I used to sew and gave up due to lack of patience and skill, but felt inspired to dust off my sewing machine again. Here’s a little something that I worked on recently:

Which sleeve looks more flattering?


H&M; Blazer.  Left sleeve (on me) slimmed & shortened, right sleeve unaltered.

When I initially tried on this blazer, I almost left it behind. I loved the light gray material and slim torso, but did not love the lack of lapels, the much shorter back, and the unsightly wide and bunchy sleeves. My other gray cascade jacket had the same sleeve issue, but it was unexpectedly sold before I even considered alterations. My current tailor charges $25 for shortening sleeves, and $20 for slimming (hopefully less for both done together).


I’ve done simpler alterations in the past such as slimming shirts and taking in the waist on a skirt. Never had I worked on a blazer, and especially not one with lining. I gingerly took apart one sleeve and tried to learn by retracing the steps of how it was assembled. As you can see in the above pics, such an alteration can make a tremendous difference in the overall silhouette of a garment.


I think I got the hang of it after one sleeve, and took step-by-step photos the second time around. Warning: Please note that I am an amateur and I’m sure there are better and more efficient ways to do this. The remainder of this post is picture-heavy and sleeve-focused so continue scrolling at your own risk of dozing off…

How To Alter Blazer Sleeves

1. If you’re not an experienced sewer, start with an inexpensive blazer that you won’t weep over if you accidentally slice or botch it. Turn the blazer inside out and use a seam ripper or sharp scissors to take apart a few inches of the lining seam (enough for your hand to fit inside comfortably). Make this hole about a few inches above the sleeve opening.


2. If you are only slimming the sleeves, then the side hole made in step 1 is all you need. If you are also shortening the sleeve length or only shortening the sleeve length, then take apart the seams connecting the lining to the outer material.


3. While the blazer is still inside-out, push the sleeve lining up near the shoulders and out of your way.


4. Measure a blazer that fits you well, and mark the one being altered with fabric chalk. Note that sleeves should not be the same width from top to bottom. It should be wider at the armpit opening and taper down by the wrist. I marked the following using a Theory blazer as a guide: 5.5″ across by the armpit, 4.5″ across by the elbow, and 4″ across at the wrist opening.


5. Use a rule or straight edge to draw a fluid line, then pin. I hate using pins and always stab myself, but they serve to keep the two layers of fabric from moving around.


6. SEW in a uniform stitch along the chalked/pinned line. Remove pins before they get near the machine.

7. Trim off the excess leaving about half an inch beyond the stitch, otherwise the extra material could look bulky. If you have a serger, you can use it now to prevent the raw edges from fraying, or do a zig zag stitch on a regular sewing machine.


8. Iron down the freshly trimmed edges from the inside and then also from the outside. Ironing is critical to sewing. If this seam was not ironed down, then it will not look crisp and smooth from the outside.


9. Measure out your ideal sleeve length, trim then fold down the material, and iron to keep it in place.


10. Pull the lining back down and trim off the extra length as well. Leave about an inch of length between lining and the end of the sleeve, fold the lining under, and then iron to keep in place.


11. Now our sleeve and lining are ready to be joined. This was the trickiest step for me. Using one hand, go THROUGH the hole we created in step #1 to carefully pin the edge of the lining and the raw edge of the outer material together. Make sure the pin is not poking through the inner lining NOR the outer material.


You can see my pins through the lining. Do this going all around the wrist opening.


12. I have no idea how to clearly describe this next step. Insert your hand again through the hole created in step #1, and pull the raw edges of the outer + lining (should be pinned together) THROUGH the hole.


13. After you pull the entire wrist through the little side hole, it should make a full circle. Sew along the pins.


14. After you’re done sewing around the circumference of the sleeve opening, insert the end of the sleeve back through the side opening, so it’s back to normal. Steps 9-13 are how I joined the lining to the sleeve without any visible stitching from the outside.


15. Now, try on your blazer. Re-do the sleeve width or length if necessary, always ironing it smooth afterwards. Once you are satisfied with the alterations, we can close the little lining hole made in step 1. At this point I was too tired to learn an invisible stitch, so I just used pink thread and stitched the lining shut from the outside.


16. Lastly, (optional) I secured the sleeve length with a light hand stitch using the same colored thread.


All done! Phew! I will show the completed garment soon.
Readers – Do you do your own alterations? If so, please share some tips or links to good tutorials.

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When you purchase through the links on this blog, I may earn a commission. Thank you for your support!

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