Have you done more than just cast on? The cast on row isn't as large as the finished project, so maybe you need to work a few inches and then measure it. And even if you're using larger needles, if the yarn is thin it may not come out as large.
Well, I am not expert but I don't think casting on 64 stitches will go very wide no matter how big the needles or the yarn. That is just my thought. Maybe it could be a table scarf?
Recent FO:Damask just needs a handle and some waxed cording.
3 pair of clogs
OTN: Wonderful Wallaby for dd(on hold)
Pigeldy done but needs to be seamed and felted
Thorne market bag
Clogs (to replace shawls)
In line to be cast on:Clogs (2 more pair)
scarf for ds
cat scarf for ds#2
2 booga bags
Are you sure you're using the right yarn and needle size? 64 stitches with worsted weight on a size 10 needle will be approx 20 inches long or so. But if you were to use several strands of a bulky on size 17 or 19 needles, you'd be approaching a lap sized afghan size.
Is the pattern online somewhere where we can have a look at it?