I did some research regarding the number of calories used per mouse click. What I found is a pile of dog ****. Every article I found refers to a report called Convert Anything to Calories. The math shown in this report shows that a single mouse click (assuming your index finger is a specific mass and your muscle contracts fully) burns 1.42 calories. Let me explain how terribly inaccurate this is.
Let's Look At Some Real Numbers
Now according to these numbers I should have burned around 10,618 calories (counting only my mouse clicks). And yesterday I burned 16,057! I must be some kind of super fueled human. Or wait... these calculations regarding calories are WAY OFF.
Now let's pretend these calculations are correct and I'm only contracting my muscles 10% of the way. If that is the case I should have only burned 1,061 calories today. Now that sounds reasonable EXCEPT that I also pressed 18,638 keys (mechanical keys I might add!). On top of all that I walked around the house, did some dishes, used the bathroom a few times, and played guitar for about 30 minutes which exerts plenty of forearm/finger muscle.
Now the finishing blow (last bit of evidence)! I have only consumed around 1,000 calories today and yesterday I only consumed about 1,200 calories. My point has been made. Clicking and typing definitely does burn calories but nowhere near 1 calorie per click.