I have been making this style of pants for a few years now. I have never given them a name and I do not have a pattern for these. No one pair is alike as I decide on the finished pants according to the sweater or shirt. I just cut and sew.
Hopefully I can show you all just how I make these. Enjoy and have fun.
First, measure the inseam of the pants you already use for your baby. If you want the inseam longer, add an inch. My boy is 7 months and his inseam is around 9″.
These style of pants are made with the arms of a sweater or shirt. I am using a wool sweater for this tutorial. Cut off the arms at the top so you have as much material to work with as possible.
First, line up both arms, one on top of the other. I align the seam in the arms to the inside of the legs. Start with the “inseam” measurement and make a mark with your scissors or pin of what will become the inside crotch area . As shown above!
For the rise (length of measurement above the inseam) I add about 8″ giving me a total of 16″. [ for my 7 month old I make the total inseam and rise length between 16" and 18"] I then cut a curve from the previous inseam mark to not quite the center of the top of the arm piece. As shown above!
Next the center crotch Panel…..
Take the off-cuts from the arms and line them up. Cut away the bottom scrap. With the pieces still lined up try to cut as large a rectangle as you can to create your crotch panels. You can decide how wide you want your center to be.
Now take one leg panel and line up the seam of the crotch panel to the inseam of the leg and pin into place. Pin the crotch panel into place along each side of the cutout in the leg. Don’t worry if the panel is a bit shorter or longer at the top as this will be trimmed even later..
Serge the panel to the leg piece. Then go through the same process for the opposite leg. Hopefully the photos shown above will help you see the steps.
I am using the turtle neck portion of this sweater for the waistband. If you do not have this in your sweater, cut out a panel from your sweater or from another.
I like my waistband at least 2″ high or higher. This is cut with a 4″ height so when I fold it, I get 2″. Make sure the waistband is the same length as the opening at the top of your longies.
Serge them together, and your longies are finished.