Why does this happen with my knitting please?

[Titsalinabumsquash]

I don't know if I'm doing something to stretch the wool but. My sidings for things are all out and I'm not sure why.

For instance it says on the wool packet that for a 10cm x 10cm square you need 30 stitches and 30 rows (just an example)

If I cast on 30 stitches and knit my 30 rows I am ending up with more like a 14x14cm square (measuring with a tape measure) is this something I'm doing wrong? Should I just cast on less stitches to get the right size.

Stupid question probably but are you using the same size needles as stated for the 10 x 10cm?

Either you are using bigger needlesnor you just have loose tension when you knit.

Sounds like your tension is too loose, try pulling your stitches tighter and you might get the correct sizing.

It may be that your tension is looser than the standard guidelines. Not really a problem, but you can try going down a needle size and see if you get the size they suggest

This is exactly why you need to knit the tension square before starting on the garment! Are you using the yarn suggested in the pattern. If yes, you might like to read this:
www.ukhandknitting.com/tension.php
it will explain it all. Basically, your knitting is too loose - you won't be able to correct this by trying to knit tighter, because everyone has a natural tension. You can correct it by using smaller needles, and knitting another tension square, and keep doing this until you get the right number of stitches and rows (stitches more important than rows).
HTH

It's very very very hard to consciously pull the stitches harder. You could easily loosen your tension later in the garment and end up with it uneven.

Knit naturally, but adjust your needle size to get the right tension. For loose knitting, a smaller needle size.

Fab! I am using the right size needle but will go down a size to see if it helps.

I rarely do a tension square but when I do I knit more than the stated number of stitches and rows. For example, if the pattern indicates 30 stitches and 30 rows to 4 inches I cast on 35 stitches and knit 35 rows. Then I measure away from the edgings; this makes the measuring more accurate. I have a kind of set square ruler thing which is brilliant. If you don't have one try using a ruler rather than a tape measure.