We can't tell without more info:
What's the position of the weld going to be? "Linear" or short lengths or going around corners and around pipes? Seam welds? Who's going to do the tack welds and fitup? A fitup weld might takes many tack welds, each of which uses a 1/2 inch to 1" of rod. All tack welds have top be re-welded over with the final weld, and that adds more needed rod.
Field or shop? In your shop or somewhere else?
What's the size of the weld (fillet or buttweld?) rather than just size of the rod?
How "good" are your welders (Newbies? Experienced? Foreign? Overseas? New hires? Temporary (shop hires or temp job shop)? Will they "work hard" to save every spare inch of rod, or will they be wasteful but faster?
If the welders have to "bend" the rods due to limited space or restricted access, each rod may lose as much as half its length.