[NoLifeKing]

You can use this to roughly calculate your RMR: http://www.caloriesperhour.com/index_burn.php

That's how many calories your body burns just by doing vital functions: heart beat, breathing, blinking, EXISTING. Eat anything less than that amount per day and you will lose weight.

Use this calculator to get a rough idea of how quickly you will lose weight if you eat x-amount of calories per day: http://www.losertown.org/eats/cal.php

I'm 5'8'' and 115lbs. I used to be around 175lbs at one point. What you want to do is certainly achievable. Good luck to you!