It depends on what you put into it. Here are the basics of what go into common milkshakes. Take the ingredents that you use, and try to figure it out accordingly.
Banana = 100 calories
Milk = 130...
There are 400 calories in one pound of peeled bananas and 25 calories in each ounce or 28g of peeled banana. For the calories in bananas by size (small, medium, large, extra large, in inches), see...
There are:
approximately 25 calories in each ounce or 28g of edible banana.
For the calorie content of other fruits and a calories in fruit chart, which you may print out if you wish to and use...