Loan-to-value is a math formula that represents the relationship between how much a home is "worth" and how much money is borrowed against it.

Loan-to-value is often abbreviated as "LTV" and is one of the many factors that lenders consider when underwriting a mortgage application. 

The math formula is straightforward:

In the LTV equation, Loan Size is the amount of money borrowed from the bank and Home Value is the lower of the home's purchase price or appraised value.

Home loans with low loan-to-value ratios are usually less risky for banks.  This is one reason why mortgage rates tend to be more favorable for home buyers and homeowners when their respective LTVs are low.

Typically, a "low" LTV loan is one in which the loan-to-value is 80 percent or less.  In some instances, however, 70 percent is considered "low".  The cut-off point depends on the mortgage lender and the mortgage product.

On a home purchase, the one way to lower LTV is to make a larger downpayment, thereby reducing the LTV equation's numerator.  Buying a home for below-market value would not reduce LTV, for example, because the purchase price would be used as the equation's denominator.

On a home loan refinance, the denominator is always the home's appraised value.

John Topa, First Sunrise Mortgage, Northeast PA Mortgage Advisor. www.FirstSunriseMortgage.com