Knowing exactly the right time to refinance your mortgage would require a bit of psychic ability on your part. That's why many experts say if you find a good deal that saves you a significant amount of money, it's probably not worth trying to beat it by predicting mortgage-rate moves.

So what rate would you need before refinancing makes sense? That's what this worksheet is designed to tell you. One thing to keep in mind, though: The interest rate isn't the only thing to consider when shopping for a new loan.

Refinancing, after all, isn't free. There are the bank fees, the bills for a new appraisal and inspection, your lawyer's fee you name it. This worksheet will help you figure out how much you'll save on your monthly payments with a lower rate and how long it will take, given those savings, to repay the cost of getting a new loan.