Each hexagon measures approximately 5.5” across, and the border is 1” wide. The blanket pictured requires 32 full hexagons and 6 half hexagons, and measures 29.5” wide by 37.5” long.
The blanket is modular, so you can adjust size by working more or less hexagons.

DK weight yarn
20 yds per full hexagon; 10 yds per half hexagon
sizes illustrated require 700 (1080, 1540, 2700) yds for
hexagons plus 150 (190, 220, 300) yds for border

US #6 / 4mm (or as required to meet gauge);
16” circular needle and DPNs for hexagons one or two 60” circular needles for border x

22 sts & 40 rounds / 4” in garter stitch; knit a single hexagon, block and measure to check finished size and drape of the fabric