A safe minimum anchor rode length in normal weather conditions is a 7 to 1 (rode length to depth) ratio, or 5 to 1 for an all chain rode. "Depth" in this case is the actual depth of the water at high tide, plus the height of the anchor hawser above the water's surface. (Scope = [water depth + hawser height] X 7). So if high water is 20 ft. deep, and your bow roller is 5 ft. above the water, you'll need to use at least 175 ft. (25 ft. X 7) of line-plus-chain anchor rode to anchor. It's a good idea to have your anchor rodes marked off in ten- or twenty-foot increments to facilitate reading rode length as you feed it out. If you anticipate a blow, a ten to one scope isn't too much to pay out. To the extent that harbor space permits, the heavy weather rule is the more scope the better! Remember that putting out too little scope is one of the most common mistakes skippers make when anchoring. Later, they wonder why their boat dragged up onto a lee shore during a squall!