how many calories do we lose when we ......?

Question

how many calories do we lose when we masterbate

Answer 1

How many calories you burn during ANY sort of activity depends on how much you weigh. This calorie burner chart does not include masturbation but maybe you can use one of the sex categories to get an idea:
http://www.fatburn.com/free_tool_activity_burn.asp

On a side note, you will not lose enough to make an impact if you are trying to lose weight.