The number of calories in a plain bagel with cream cheese depends on the size of the bagel, as well as on the amount of cream cheese you use. Because cream cheese is high in fat, going overboard can make the calories add up quickly. Use just 1 tablespoon, and look for low-fat cream cheese to spare yourself even more calories and fat.
On average, a plain, medium bagel that's 3.5 inches in diameter contains 270 calories, while a small, 3-inch bagel has just 177 calories. One tablespoon of regular cream cheese has 50 calories, while 1 tablespoon of low-fat cream cheese has just 30 calories. Therefore, a medium bagel with 1 tablespoon of cream cheese contains 320 calories, while a small bagel with 1 tablespoon of low-fat cream cheese contains 207 calories.