Divide your total refinance costs by your monthly payment savings. The answer is how many months it takes to earn the cost back. If a refi costs $3,600 and drops your payment by more than $100 a month, you recoup the cost in under three years. Whether that clears the bar depends on how long you plan to keep the loan. On the rate side, our quick rule of thumb: divide $125,000 by your loan amount to get the rate improvement that generally justifies a refi. - On a $250,000 loan, about half a percent. - On a $500,000 loan, closer to a quarter percent. - On a $1 million loan, sometimes as little as an eighth. Bigger balances clear the bar with smaller rate drops because the dollar savings are larger. Closing costs swing the answer too, and they vary a lot by state (title and transfer taxes can run a few hundred dollars in one place and several thousand in another). One way to sidestep the payback question entirely is a no-cost refinance, where a lender credit covers the costs, so the lower payment starts immediately and you can refinance again later if rates improve. If you want us to run your actual balance and costs against that math, that is a quick Roadmap conversation.