I am working a dish cloth pattern that says to cast-on 39 stitches, using a US 6 needle. I will be using a US 9 needle, because I am using a heavier weight yarn than the pattern uses. How many should I cast on?
The pattern is as follows:
ROW 1: KNIT
ROW 2: k3, yarn forward, slip one stitch purlwise, yarn back. Repeat across until you have 3 stitches left on the needle and knit those 3.
Repeat rows 1 & 2 until the cloth is a square.
I would just try something until it works, but I’m terrible like that…
Would it be 35 or 31?
What yarn weight does the pattern recommend and what yarn weight are you planning to use? Does the pattern give a gauge?
Worsted weight for the pattern and I am going to use bulky.
i did some digging and some math. if they asked for worsted and size 6, then the intent was for a tight/thick finished stitch. size 6 is normally for dk/light worsted. anyway, whether it was dk/light worsted, or regular worsted they specified in the original, it would give you a range of 6.5"-9.75" for your finished size (with needles from 5 up to 9). with you doing bulky and size 9, you’ll get about 3-3.75 stitches per inch… so depending on size of FO you want…:
1"= 3-4 sts
2"= 6-8 sts
3"= 9-11 sts
4"= 12-15 sts
5"= 15-19 sts
6"= 18-23 sts
7"= 21-26 sts
8"= 24-30 sts
9"= 27-34 sts
10"=30-38 sts
all rounded down/up to the nearest full number, and all depending on your own knitting gauge… hope that helps - X 
[COLOR=“Purple”]YEP!!! 31 & 35 work, and it’s turning out beautifully!!![/COLOR]