Yarn substitute question

the pattern calls for 336 yrds:

4 skeins 1824 Cotton from Mission Falls,
(50 gr skein/84 yds)
Size 7 or 9 knitting needles
Gauge: 18 St in pattern = 4.5 inches

the yarn i want to use

3 - Light: DK, Light Worsted Yarn
2.50 oz./70 g (168 yd/154 m)
100% micro-fiber acrylic
Knit: 24 St sts + 32 rows = 4" (10 cm) on size 4

so i guess i am wondering, if i knit on 7US with the yarn i want to use, how much yardage will i need? the same? more? less? if i use 7’s will it be a more open weave(its a feather and fan pattern poncho)…

[size=7]tia :notworthy: [/size]

Yes, it will be more open. You may want to use a needle size in between, like 5 or 6 and see how close it is to the gauge of the pattern. If it’s not too open and you like the fabric it makes, you’ll have to CO more stitches.
sue