Mortgage lenders use FICO scores, calculated from your credit report. The score reflects payment history (35%), amounts owed (30%), credit history length (15%), credit mix (10%), and new credit (10%).

Conventional loans typically require a minimum 620 score; FHA loans accept scores as low as 580 (with 3.5% down) or 500 (with 10% down). Higher scores qualify for lower interest rates.

A jump from 680 to 740 can lower your rate by 0.25-0.5% — on a $400K loan that's $50,000+ in interest over 30 years.