I know that there are converters online somewhere, but I don't use them. If you are good at math, all you need to know is you multiply the amount of the fabric count--yours is 11--by the measurements of your fabric---so the stitch count for 12 by 18 fabric would be 132 by 198 11 x12 =132; 11 x 18=198
Hope that makes sense
Most of the online converters I'm finding are the reverse of what you want. The information I gave you works out fine, but if you want to leave fabric for a border then you'd have to take that into account too. Allowing for a 2 inch border on all sides would take the stitched area down to 8 by 14, so then your stitch count would actually be 88 by 154.
I hope I haven't confused you
Work in Progress
Dimensions Passion Flower Angel
Tempting Tangles Welcome SAL
Various small designs
Glad to help--sure wish they'd make it easier to find that online--it's easy enough to find the reverse of what you want though. I'm just glad I'm sufficient at math to sort it out--guess I'd better be, as I used to do volunteer tutoring in math at my son's schools
Work in Progress
Dimensions Passion Flower Angel
Tempting Tangles Welcome SAL
Various small designs
has a stitch to inch but not a inch to stitch.
Although can sort of use the the chart in a backwards way by finding the count and then looking at the closest measurment then seeing an estimate of how many stitches it will be...but not exact.