Gauge and needle size

Hello all, I have a question about gauge and needle size. I have a pattern that calls for size 6 needles and 17sts/4 inches. Just finished my swatch and it measured 20 sts/4 inches. I was thinking of going up to either a size 7 or 8 needle but wanted a second opinion as I am not the most seasoned knitter. Thank you!

Try them both. You don’t have to do separate swatches, just knit a couple rows of garter to separate them.