Interest Cost

Interest Cost (IC)

A comprehensive and time-adjusted measure of loan cost to the borrower.

IC on a Mortgage: IC is what economists call an “internal rate or return.” It takes account of all payments made by the borrower over the life of the loan relative to the cash received up front. On a mortgage, the cash received up front is the loan amount less all upfront fees paid by the borrower. On an ARM, IC captures the effect of interest rate changes on the monthly payment and the balance, but future rate changes must be assumed.

Formula: IC is (i) in the formula below:

L - F = P₁ + P₂/(1 + i)2 +… (P_n + B_n)/(1 + i)n
Where:

L = Loan amount

F = Points and all other upfront fees paid by the borrower P = Monthly payment

n = Month when the balance is prepaid in full

Bn = Balance in month n

IC Versus APR: IC differs from APR in the following ways: IC is measured over any time horizon, whereas APR assumes that all loans run to term. IC may be measured after taxes whereas APR is always measured before taxes. On an ARM, IC can be calculated on any interest rate scenario whereas APR always uses a no-change scenario.