A lot of calories can be burned climbing stairs. The number will depend on how many stairs you climb and how fit you are.
The more fit you are, the less calories you will burn while climbing stairs. The number of calories burned is really contingent upon how many stairs you climb and how high your heart rate gets. The more in shape you are, the harder you have to work to get your heart rate up. When your heart rate is up, you are burning some serious calories.
Many people trying to lose weight, opt to climb the stairs in a building rather than taking the elevator, in an effort to burn more calories. If you are climbing up several flights of stairs and are reasonably fit, you can burn about 150 calories. Of course, this number greatly varies depending on how fit you are and how many stairs you climb.
A good rule-of-thumb is to remember that if you were to climb up stairs for one hour straight, you would probably burn close to 400-500 calories depending on your speed and heart rate. The faster you go, the more calories you may burn because your heart rate will increase.
If you take your time going up the stairs you will burn less calories. Move quickly and watch the calories be burned from climbing stairs.