Best real estate refi calculators

Despite reliability, most overlook 5 key situations

By Inman News Feed
Add Comment Add Comment | Comments: 0 | Posted Feb. 28, 2011

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Despite reliability, most overlook 5 key situations

Jack Guttentag
Inman News™

Editor's note: This is the second of a two-part series.

In the first article of this series, I suggested that the net benefit of a refinance to the borrower should be measured by the net present value (NPV) or net future value (NFV) of all benefits and costs. Whether the refinance increases or decreases the rate at which the loan balance is paid down is an important but often overlooked benefit or cost that should be captured by a refinance calculator.

Testing calculators

I use two examples to test how a calculator works. In one I assume a significantly lower rate on the new loan and low refinance costs, but the new loan carries a 10-year term and therefore a higher payment than the old loan. The calculator should recognize that this is a great refinance for the borrower who can afford the new payment because of the rapid paydown of the balance.

In the second test scenario, the new loan has a higher interest rate than the old loan but because the new term is much longer than the remaining term on the old loan, the new payment is lower. The calculator should recognize that unless the borrower needs the lower payment to avoid default, the refinance is a loser because of the much slower reduction in the balance.

Early Web-based calculators

I first looked at Web-based refinance calculators about 10 years ago when I found a fairly consistent error in most of them. They defined the breakeven period as the cost of the new loan divided by the reduction in the monthly mortgage payment. In my first test scenario, they erroneously told borrowers that this refinance was a loser.

This approach panders to the preoccupation of many borrowers with the monthly payment, and it is wrong. It totally ignores differences between the old mortgage and the new one in how rapidly the loan balance is paid down.

Current Web-based calculators

Recently, I set out to see what difference 10 years has made. To select the sites, I entered "mortgage refinance calculators" in Google and examined the first 10 that appeared. These are among the most widely used calculators, and several of these sites are in the business of licensing their calculators to other sites. and continue the erroneous practice of measuring breakeven as the ratio of refinance cost to payment change. These are very good websites, but don't use their refinance calculators. uses total interest payments as its sole measure of the net benefit from refinancing, which also ignores changes in the balance. This site, furthermore, considers the down payment to be part of the refinance costs, which is nonsensical. Don't go near this calculator. has a payment calculator only and should never have come up in my search.

Five sites calculated the breakeven period as the ratio of refinance cost to the cumulated monthly interest savings, a measure I had never seen before. After dissecting it, I concluded that this measure is not as good as NFV because it does not explicitly take account of differences in balance paydown, but it does do it indirectly and the error is small.

Those five sites are:

These are all acceptable calculators.

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