Updated: 3:42 p.m. ET

Menu labeling is supposed to help us make more informed food choices, but new research shows consumers consistently underestimate the calories in Chipotle burritos.

In a new study published in the journal Public Health Nutrition, researchers surveyed 326 Chipotle customers about what they ordered and how many calories they estimated were in their order. They found that on average, the customers underestimated the calories by 21%. For example, on average, the customers guessed their burritos were about 630 calories when they were closer to 900.

Chipotle calorie counts for burritos can range from 350 to 970, and that’s confusing for customers placing orders. A burrito with just beans is the lowest calorie option, and a burrito with all the stuffings, like sour cream, meat and guacamole, has the highest amount. When the researchers explained this to the customers, they became much more accurate at guessing the calories in their burritos, suggesting more transparency is helpful.

Since the Affordable Care Act is requiring restaurant chains with over 20 locations to provide calorie information, the researchers conclude that offering customers more information about what ingredients are higher in calories is the best way for them to make informed eating decisions.

Chipotle says the requirement is a bit harder for them to stick to than other fast food restaurants, since there are 60,000 ways to put an order together. “The degree to which people may misestimate calories is really a product of a menu labeling law that doesn’t work so well for a restaurant like ours,” says Chris Arnold, Chipotle’s communications director. “Putting calorie counts on things is super easy when it’s a packaged product and it’s made exactly the same every time or it’s a restaurant where you order a number one and always get exactly the same thing.”

To make the ranges, Chipotle takes the simplest option—tortilla and a bean—and lists the highest calorie option for that order. For instance, the burrito range starts at a tortilla and pinto beans, instead of the lower calorie black beans. “We recognize it’s not ideal, but there’s not really a better way to do it when you can put it together in so many different ways,” says Arnold. Chipotle also sells more burrito bowls than it does burritos.

If customers visit Chipotle online, they can use a nutrition calculator to add up all their toppings.

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