A calorie is a measure of how much energy the nutrients protein, carbohydrate, and fat can supply your body. One gram of fat supplies 9 calories. So, in order to answer your question we first have to convert one pound into grams.

1 pound = 453.6 grams

This means that one pound has 453.6 x 9 = 4082.4 calories.

I hope this answers your question.