You need only take a look at the physique of the late, great Luciano Pavarotti to guess that the answer to the question: ‘how many calories do you burn by singing’ is ‘not many’. When we sing, we exhale more air than usual through our lungs, through our larynx to make our head and body vibrate to amplify the sound. Professional singers learn to project their voices by training their abdominal muscles and diaphragm, rather than using only their vocal chords to change the sound they produce.
Some studies have been conducted to measure whether there is a significant amount of energy expended through the act of singing. These studies all pointed to the fact that there is a very slight, and not always detectable, calorie consumption produced through the act of singing. The most quoted study, performed on a group of children ages between 9 and 11, in 1949 showed that there is no difference between singing, or just breathing normally, within the limits of error of the experiment.
Any mild energy toll is accounted for by the extra exertion of taking deep breaths and tightening the stomach muscles. If you wish to burn calories by singing, make sure you stand up during your practice, as you will burn more calories in this position and sing with more strength.