The proprietary credit score model from Fair Isaac Corporation, used by most mortgage lenders.
FICO scores range from 300 to 850. There are multiple FICO models — mortgage lenders typically use FICO 2, 4, and 5 (one from each major credit bureau).
FICO scores are calculated from: payment history (35%), amounts owed/credit utilization (30%), length of credit history (15%), credit mix (10%), and new credit inquiries (10%).
The 'mortgage trio' score is the median of your three bureau scores. If a co-borrower applies, lenders use the lower of the two median scores.