The whole decision is one number: break-even
A refinance is a purchase. You spend real money today — closing costs — to buy a lower monthly payment, and the deal only turns profitable once the accumulated savings pass what you paid. On the default example, a $320,000 balance at 7.25% with 25 years remaining costs $2,312.98 a month. Refinancing to 6.25% over the same remaining term drops that to $2,110.94 — a saving of $202.04 every month. Against $5,500 in closing costs, the break-even lands at about 2 years 4 months.
That single number carries the whole decision. Stay in the home for seven more years and the deal earns roughly $55,000 after costs. Sell in year two and the same “great rate” loses money. Before anything else, be honest about how long you expect to keep this loan — not this house, this loan, because a future refinance restarts the clock too.
The term-reset trap
Most refinance offers quote a fresh 30-year term, and that is where the marketing does its work. Take the same 6.25% offer, but spread over 360 months instead of the 300 you have left: the payment falls to a seductive $1,970.30. The cost hides in the total: lifetime interest of $389,306, versus $313,283 when you match your remaining 25 years — about $76,000 more for the privilege of a payment that looks $140 cheaper.
The fix is simple: when you refinance, ask for a term that matches what you had left, or keep the new 30-year loan but pay the old amount every month. Both capture the rate cut without re-renting the amortization curve’s expensive early years. This calculator lets you set the new term to anything, so run both versions before signing.
How big a cut is actually worth it
The folk rule says refinance when rates drop a full point. The math is more nuanced, and the break-even line tells you why. A half-point cut to 6.75% on this balance saves $102.07 a month and needs about 54 months to recover the same $5,500 in costs — nearly double the wait of the full-point cut. Whether that is fine depends entirely on your horizon.
Balance size bends the rule too: the same half-point on a $600,000 loan saves roughly twice the dollars, halving the break-even. Big balances justify small cuts; small balances need big ones. And shop the closing costs as hard as the rate — every $1,000 shaved off costs cuts this example’s break-even by about five months.
What this estimate deliberately leaves out
The comparison isolates principal and interest. Escrowed property taxes and homeowners insurance move with your home, not your loan, so they are excluded from the payment difference. Discount points, lender credits, cash-out amounts, and the tax treatment of mortgage interest are not modeled — each can tilt a close decision. And the payment on a new loan can be estimated to the cent, but qualifying for the quoted rate depends on your credit profile, equity, and documentation. Treat the output as the decision framework and your lender’s Loan Estimate as the contract-grade numbers.
Frequently asked questions
When is refinancing a mortgage worth it?
When you will keep the loan past the break-even point. On a $320,000 balance, dropping from 7.25% to 6.25% over the same 300-month term saves $202.04 a month; with $5,500 in closing costs, the refinance pays for itself in about 2 years 4 months. If you might sell or refinance again before then, the deal loses money no matter how good the rate sounds.
Why does restarting a 30-year term cost so much?
Because you re-spread the balance over more years at the point where your payments were finally attacking principal. Taking the same 6.25% offer over 360 months instead of the remaining 300 drops the payment to $1,970.30 — but lifetime interest rises to $389,306 versus $313,283 if you match your remaining term. The "lower payment" quietly costs about $76,000 extra.
What do refinance closing costs include?
Lender origination fees, appraisal, title search and insurance, recording fees, and prepaid escrow items. They commonly run a few percent of the loan amount. Ask for the standardized Loan Estimate from each lender — it makes the fee lines directly comparable.
Is a "no-closing-cost" refinance really free?
No — the costs are either rolled into the loan balance (you pay interest on them for decades) or absorbed through a higher rate. It can still make sense if you expect to move soon, because you avoid the upfront hit; run this calculator with the higher rate to see the trade honestly.
How big a rate cut justifies refinancing?
The old "one percent rule" is a decent starting point but the break-even math is the real test. On this example, a half-point cut to 6.75% saves only $102.07 a month, pushing break-even to about 54 months — fine if you will stay 10 years, poor if you will not. Larger balances justify smaller cuts because the same percentage saves more dollars.