I’m going to make a vest for my son-in-law. The pattern is in pieces but I want to do it in the round. Any thoughts on this? How do I convert the pattern to in the round? Is there a simple conversion to use? This is the pattern I’m using and I’m making the smallest size.

You will cast on the total number of front and back stitches and knit those main body stitches in the round. You may wish to eliminate the edge stitches which would be taken up in the seam.
Be warned - when you reach the armholes you will have to knit the front and back separately, flat.
So funny - one time I forgot and there I was all the way up to the shoulders! I don’t know what I was thinking.

@Regina , welcome!

You’ve already received great advice above.
I’ll just add that you might want to write out your bottom-up vest pattern, with changes for knitting in the round.

For example:
With smaller needles, cast on 152 stitches, as follows:
Cast on 76 stitches in K2,P2 ribbing (19 groups of 4 stitches) for the back of the vest. Place marker (left side “seam”).
Cast on 76 stitches in K2,P2 ribbing (19 groups of 4 stitches) for the front of the vest. Place marker (right side “seam”, beginning of round).

Work in K2,P2 ribbing for 2-1/2 inches (6cm).
(Note: the pattern shows increases in last row of ribbing, but might want to do this in first row of stockinette.)
Increase 6 stitches evenly across row; 3 across the back and 3 across the front:
((Knit 19, make 1) x 3, Knit 19, slip marker)) x 2.
Now have 158 stitches on needles (79 for the back, 79 for the front).

Change to larger needles and proceed in stockinette stitch until work measures 15" from beginning. . .

Thank you so much for this!!! So helpful!! I will do this and may come back for help again after the 15 inches!

@Regina - sounds great, happy knitting!
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