What does UPB mean in real estate?

What is UPB?

In real estate, UPB stands for Unpaid Principal Balance. This term refers to the portion of a loan, such as a mortgage, that has not yet been repaid to the lender at a certain point in time. Initially, the UPB is equal to the amount borrowed, and it decreases as payments are made over the life of the loan. The UPB is how much is still owed on the loan principal at any given moment, excluding any interest or other fees that may also be due.