Hello, I am making afghans for my granddaughters and one needs widening. I have never run to that problem before and am looking for a solution

[Shuggy]

Please see above. 

[Granny Square]

You are not going to like what I'm about to say....

If you have used the same yarn for both, and the same pattern, and the stitch count was the same, the only thing I can think of is that you grabbed a too-small hook for the narrow one. 

Measure the number of stitches across 4", and count the # of rows that comprise 4" of the blanket that is 'right', and measure the same on the one that was 'too narrow'.  Presumably the narrow one has more stitches across 4", and more rows 4" high, which would mean that your stitches were smaller on the narrow one. 

I assume you have already counted the stitches across both blankets and determined that both have the same number of stitches, but if you haven't, and discover the smaller one has fewer...

Either scenario I'm guessing at means you are going to have to rip the narrow one out and start over, but first swatching to make sure you have the right hook to get the same # of stitches across 4" and the same # of rows in 4" as you did in the 'right' blanket.

 

[Robin55]

No worries. Add a border to make it wider. 

[Tampa Doll]

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I usually add a border, not only will it widen the blanket, but it will make it different from the other one.

[Granny Square]

I originally suggested a border before hitting post, but deleted it before posting and re-wrote my answer, because I assumed that they might be a pair, if not identical likely same pattern but different color scheme perhaps, and it would be an obvious 'patch'. You would have to put a border only on the 2 sides, which IMO would look strange.

To add a border that is logical and that doesn't scream "I goofed", on the too-narrow one you'd have to make the second make it shorter by the same measurement it is too narrow by, then make a border all around to reach the side of the first.

Example, if the second blanket is 6"  too narrow, also make it 6" too short,, and add a 3"  border all around which will make it match the other size-wise.