Burn 3500 calories over for lose one pound of fat. If you want to burn 3500 calories in one day , you must go to step by step .

Step 1:
First of all calculate your BMR  i.e  Basal Metabolic Rate . Our body needs to maintain general functions like breathing and digestion. You should need to eat minimum number of calories per day.

Step 2:
By using calorie calculator calculate the how many calories burn while sitting, exercising , lifting weights, walking etc. in a day. It helps you to keep your activity level normal.

Step 3:
Calculate how many calories you eat in a day. It is calculated by using online websites like calorie count and also by wearing a heart rate monitor which calculates  burned calories.

Step 4:
Finally take your BMR number and add it into your activity calories and then subtract your total food calories. If you are eating more than burning then you will gain weight and if you are burning more than eating then you will lose your weight.