around how many calories should i eat per day to lose around a pound and a half every week?

Try 1500 calories. The aim is to lose roughly 1lb per week.

Part of this depends on exactly how active you will be.  

The body needs about 1500 calories just for basic body functions.  Your body at rest will still burn about 1500 calories just because of the heart beating, the lungs functioning, and all the other body parts that do things even when you aren't actually moving.

Therefore, the minimum amount you should eat per day would be about 1500 calories.  If you are eating 1500 calories AND do any exercise at all - then the calories burned doing any activities would be what helps with your weight loss.

So - if you eat between 1400 to 1600 per day - you should drop about 1 to 2 pounds per week if you have any level of activity at all.