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Try this DIY lengthening kids pants sewing tutorial to make pants last longer! Perfect for mending hole-y knees or just adding length.

If you’re looking for creative ways to add length to pants, here is an easy sewing method! My eldest loves these bat pants, but not only were the knees completely threadbare, they were looking more like capris than pants with his ankles hanging out. I decided to take care of both problems at once by chopping out the knees and replacing them with a larger segment!

Beginner friendly, keep reading for a DIY lengthening kids pants sewing tutorial that shows you how to do the same thing! This would work well for adult pants too.

Here you can see how dire the situation was! Practically a window at this point. It would be easy to make the new knee quilted, add fun appliques on top, etc. The original bat pants are from H&M so not exactly super high quality. I don’t think the rest of the pants will last longer than another year so I didn’t want to invest a ton of time into them knowing they won’t be handed down again, so mine are boring plain black.

If you like this post, check these out while you’re here:

• Sewing tips for beginners -15 mistakes to avoid!
• Beginner sewing supplies list – what to buy on a budget!
• 20+ ways to refashion clothes that are too small
• How to mend a hole – 20+ creative inspiration & tutorials

Here is what the finished pair looks like! The edges are left raw in this tutorial, so this would only work for knit pants like leggings or sweatpants (not jeans). I happened to have another hole-y pair of sweatpants on hand to chop into, but you could also very easily DIY the insert piece with fabric yardage as well.

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Ready to try it yourself?

DIY lengthening kids pants sewing tutorial

Supplies:

• Rotary cutter [Shop: Amazon ]
• Acrylic quilt ruler [Shop: Amazon]
• Sewing machine
• Ballpoint needle [Shop: Amazon ]
• Sewing clips [Shop: Amazon ]
• Extra pair of semi-similar sized pants that are a similar weight or fabric yardage to DIY the new knee

Steps:

Step 1- First, you need to slice off the offending knee if you’re working around a hole like I was – otherwise just cut wherever you want the new section to start. Match it to the other leg for an identical chop.

Step 2- Next, I compared my sliced piece to the existing pair of sweats I had. The bat pants are a kids 12 and the black are an adult small – it worked out fine, just trying to match up widths before I cut the new knee. If you want to be careful, you can mark top/bottom and front/back with a pin or chalk here – I think with baggy-ish sweats it doesn’t matter as much but maybe it would on some styles that have significantly more fabric on the back leg piece or something.

Step 3- The most important step of this is *right sides together*. You’ll want to flip the new knee inside out, matching side seams, and clip all the way around. 

Step 4- Time to sew! Don’t forget ballpoint needles with knits and to use a stretch stitch unless they’re super baggy. Pull off the free arm if you have one and slowly sew around the opening. I used a 1/2″ seam allowance, which is large, so both feed dogs can grab the fabric no problem and top stitching will be easy. Then, pull it off and press the new seam allowance you just created up into the knee and top stitch it down.

Step 5- This is what it should look like now! Repeat on the other leg!

Step 6- Turn the lower leg inside out and nest inside the new top leg piece, clip and sew the same as previous steps. Repeat for the second leg and you’re done!

Here you can see how much longer they got, with the old knee layered on top!

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