How can find weight of a iron rod?

If I had to do it I'd cut a foot off the rod and weigh it. Then I'd simply multiply the weight of the rod times its length to find the total weight of the rod. Good luck, Tom

Depends on how big it is. The simplest solution is to weigh yourself on a scale and then weigh yourself holding the rod. Subtract the 2 and voilà! the difference is the rod weight.