Refinancing means paying off your current mortgage with a brand-new one. People do it for three reasons: to lower the interest rate, to change the length of the loan, or to convert equity into cash through a cash-out refinance. The new loan has its own closing costs, typically 2% to 5% of the amount borrowed, which is what makes the decision a math problem rather than an obvious yes.
The key number is the break-even. Suppose a rate-and-term refinance lowers the payment by $250 a month and costs $6,000 in closing costs. The break-even is 24 months. If you plan to stay longer than two years, the refinance pays for itself; if you might move next year, it does not.
A rule of thumb says a refinance is worth exploring when rates drop about one percentage point below your current rate, though on a large loan a smaller drop can still work. Shortening the term from 30 to 15 years raises the payment but cuts total interest dramatically.
Cash-out refinances turn equity into money for renovations, debt consolidation, or investment. They raise the loan balance and often the rate, and they put the house behind whatever the cash is used for.
The common mistake is restarting a 30-year clock ten years in without noticing that the new loan, even at a lower rate, means 40 years of payments in total. Asking the lender for a 20-year term, or making the old payment on the new loan, keeps the original payoff date.