3500 calories in a pound. Round up all your calories since we usually underestimate what we eat and what we burn. Take approx what you burn(exercise + metabolic) in a week and divide by 3500. If you round up your daily intake, and round down what you burn then you will usually get a realistic number.
ex (numbers not applying to you, just for show)
Say you think you burned 570 in the gym, just assume its 550
You think you ate 1600 calories in the day, let's add 100 that because we usually underestimate what we consume.
You add up your 7 days and you think you created a 3800 calorie deficit, let's say its really 3600.
You would burn about a pound, don't expect more, but expect possibly less.
Making SMALL roundings in your exercise and calorie consumption is more accurate than going to the exact number. We typically burn less in exercise than we think and consume more than we believe. It's logical to round things up and down a LITTLE to get a more accurate number.
Basically though, just divide your deficit for a week by 3500 to get your ideal pound loss.
Oh, I'll just throw this out there: If you exercise and you're female don't go under 1200, you won't feel good and it's not ideal for long term weight loss. If you're male then don't go under 1000.