Garter stitch knitting has a two to one ratio.
Now that means that you have to do twice the rows as stitches to get a perfect square.
My grey blanket knitted squares had 25 stitches and I knitted 46 rows.
So this means although they look square they are not.
To get a perfect square I should have done 50 rows because I had 25 stitches.
Well I wanted to try this out and see for myself.
And it is true.
Here are two squares I knitted in garter stitch.
The one on the left is one of my grey blanket squares so it is 25 stitches and 46 rows.
The one on the right is 20 stitches and 40 rows.
Now they may both look square but the one on the right is perfectly square.
How can you tell?
Apart from measuring it that is.
Well you can fold it into a triangle and then you can see it.
This one isn't perfectly square see the bit that is over there on the left hand side?
I didn't know this when I started making my grey blanket but I will remember it in the future.
This only applies to garter stitch as far as I know.
And it works for any sort of yarn and number of stitches, as long as you do twice the amount of rows as you have stitches you will get a perfect square.