Look for a 30-50 point drop in credit score for a 30 day late. If you continue to miss payments, your 30 day will turn into a 60 day and so on and so forth. As the payments turn to 60 or 90 day lates, your credit score will decrease even more.It's very difficult to give an exact number but be prepared that when this happens, expect your credit card limits reduced and interest rates increased.