If you’re reading this over a bowl of bran cereal with raisins and skim milk, feeling smug about your healthy diet, well, maybe you shouldn’t be so sure of yourself.

What about those added sugars hidden in the cereal? Will you eat any more fruit for the rest of the day? And how does that big slice of stuffed-crust pizza on the lunch menu fit into a balanced diet?

Starting this week, you can get answers online from a free, interactive planner designed to help Americans eat more healthfully. The program, called MyPyramid Menu Planner, lets you evaluate up to a week’s worth of meals and snacks. It’s at www.mypyramid.gov.

It’s like a customized diet adviser, calculating calorie needs and a balanced eating plan based on weight, height, age and activity level. MyPyramid, the consumer guide to federal nutritional advice, provides the foundation. The menu planner lets you enter what foods and beverages you’ll consume that day and evaluates how that diet matches up with recommendations on fruit and vegetable consumption, protein, dairy and other items. It can track up to four people.

The customized advice is an eye-opener even for people who try to follow the latest nutritional guidelines, says Brian Wansink, the new head of the USDA’s Center for Nutrition Policy and Promotion. Wansink is better known as the author of the bestseller Mindless Eating, which details why many of us eat more than we realize.

“A lot of us think we are incredibly healthy eaters,” Wansink says. “When you go and take a look at this, it’s a real wake-up call as to how much of a wishful thinker we tend to be.”

Not eating enough fruit? After the program evaluates your eating habits, it’ll recommend ways to work more into your diet. Want to lose weight? You can get guidelines on cutting calories while still taking in a balanced diet. Overindulging on extras like alcohol and fats? You’re going to hear about it.

Menu Planner is one of the first initiatives of the agriculture department’s Project M.O.M., aimed at encouraging a family’s primary food buyer to choose beans, broccoli and bananas instead of burgers and fries. Other efforts targeting the nutritional gatekeeper include monthly podcasts and guidelines coming later this year for balanced diets for preschoolers and pregnant or breast-feeding mothers.

“If you get the one person who makes a difference, that has a tremendous ripple throughout the entire family,” Wansink says.

The site does not store data from visitors, says John Webster, an agriculture department spokesman. So if you’re eating too much meat and not enough whole grains, the government won’t make a note of it.