Explain BMR, etc; how much should I eat?

cocopies

I weigh 123lbs, and I want to be around 110-115. So to lose 1lb a week, I need a 500 calorie deficit every day. But should I be subtracting that 500 from my BMR, which is 1420, or my TDEE, which 1700?

Also, is it still safe to create a 500 calorie deficit from the TDEE because then I would be eating below my BMR?

I_Will_End_You

You should subtract it from your TDEE, not your BMR. And considering you don't have much to lose, you should probably choose a 1/2lb per week and go with a 250 calorie deficit.