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.