Dietary guidelines and caloric percentages

Q. I really appreciate the dietary guidelines that you publish from time to time, but my wife and I find it hard to do the math in a busy supermarket. Can you give us targets that are easier to use than "percentages of daily calories"?

A. I understand the problem, and I'll try to help. The reason we use percentages of daily calories is that dietary needs vary from person to person. But let's do the math for a hypothetical person, and then give you a template so you can run the numbers for yourself.