Calories alone do not produce muscle. You should have a good balanced diet, a protein shake or two per day, glutamine is good, creatine, and a good free weight exercise routine.
You don't gain calories from sitting. You gain calories from eating.
A weight gain calculator is useful in determining how many calories you need to intake on a daily basis in order to gain "good" weight and build muscle.
If you gain muscle while exercising, you can gain weight, otherwise it is pretty hard to, unless you are eating too much fatty foods or too many calories.
6000
To gain one pound is 3,500 calories.
10
400 calories
The short answer is 7700 extra calories will make you gain 1kg of fat
2000
Maybe 1500.maybe less like,1200
Run many miles.
35,000 calories.