With all my previous dogs I've always just made sure their food bowl was full and they ate when they wanted. I guess it worked just fine, because I've never had a fat dog.
But Jack seems to really go through a LOT of food so I finally checked the chart on the bag and measured his bowl. The chart says he should have 5.5 or 6 cups per day. He's been eating about 16 cups per day. What a pig! It looks like I'll have to meter a dog's food for the first time.