Having trouble with sizing

Hi there,

This may be a really stupid question but ive just started my first square for a blanket. The pattern says to cast on 33 stitches using 4.0mm needles and the overall square wil be approximately 15cm square. However when i cast on im lucky if my 33 stitches measure 11cm. Where am i going wrong please? Thanks.

How does your gauge compare to that given in the pattern? You may need a larger needle if you’re knitting really tight or your yarn may be a lighter weight than the pattern is written for.