Refinance Calculator — When a New Mortgage Actually Pays
Refinancing sounds like free money: swap a 7.25% mortgage for a 6% one and keep the difference. Sometimes it is. But a refinance also restarts your loan clock, charges closing costs, and can quietly add years of payments — so the honest question isn't "is the rate lower?", it's "how long until I'm actually ahead?" This calculator works out that break-even point, which is the only number that should decide it.
The three numbers that matter
- Monthly saving — old payment minus new payment. The headline, and the least sufficient.
- Break-even months — closing costs divided by the monthly saving. Move or refinance again before this point and you lost money on the deal.
- Lifetime interest — total interest on the old loan's remaining path versus the new loan's full term. This is where the clock-reset shows its teeth.
A worked example — and it's closer than you'd think
You owe $320,000 at 7.25%, with 22 years (264 payments) left. Your payment is $2,428.46, and staying put means $321,113.09 more interest over those 22 years. A lender offers 6% for 20 years with $6,500 in closing costs:
- New payment: $2,292.58. Monthly saving: $135.88. Nice — not life-changing.
- Break-even: $6,500 ÷ $135.88 = about 48 months. You must keep this new loan roughly four years before the refinance has earned back its own costs. Sell or move in year three and the "saving" was an illusion.
- Lifetime interest: the new loan's interest totals $230,219.05 — $90,894.04 less than staying put, before counting the closing costs. That gap is real, but it only fully arrives if the loan runs its course.
- The shorter-term alternative: the same balance refinanced into 15 years at 5.75% costs $2,657.31 a month — $228.85 more than you pay now — but total interest falls to $158,316.21, and the house is yours outright seven years sooner.
The trap this example exposes: refinancing a loan with 22 years left into a fresh 30-year term would slash the payment — and can still cost you more overall, because you re-buy the early, interest-heavy years. Compare total interest and break-even, never the payment alone. If a refinance doesn't beat your current loan on BOTH, it hasn't beaten it.
When refinancing usually makes sense
- Rates dropped a full point or more below yours, and you'll stay in the home well past break-even.
- Your credit score jumped since the original loan, so you qualify for a tier you couldn't touch before.
- You're shortening the term — 30 years down to 15 or 20 — and the higher payment genuinely fits.
- You're escaping an adjustable rate before it adjusts, trading uncertainty for a fixed payment you can plan around.
- You're dropping mortgage insurance because your equity has passed 20% and the old loan won't remove it.
And when it usually doesn't: you're planning to move within the break-even window, the "savings" come only from stretching the term back out, or the closing costs are buried in a slightly higher rate that takes a decade to forgive. Cash-out refinancing deserves extra suspicion — it converts home equity into debt at mortgage rates, which is cheap money spent on expensive habits if it funds consumption.
Should you buy points? Run the same break-even
Lenders will offer you "points": pay 1% of the loan upfront ($3,200 on our $320,000 example) to cut the rate, typically by about a quarter point. On the example above, dropping from 6% to 5.75% lowers the payment from $2,292.58 to $2,246.67 — a saving of $45.91 a month. Divide the cost by the saving: $3,200 ÷ $45.91 ≈ 70 months. You'd need to keep that loan nearly six years before the points turn a profit.
So the rule writes itself: points reward people who stay put, and quietly tax people who move, refinance again, or pay the loan off early. If there's any real chance you'll sell within five years, take the higher rate and keep your $3,200. Certainty about staying is the only thing that makes points a bargain.
One more gatekeeper: the appraisal
Before any of this math becomes real, an appraiser values your home — and their number, not yours, sets the loan-to-value ratio the lender uses. A low appraisal can push you into a worse rate tier, shrink the loan, or kill the deal outright. It isn't common, but it happens most in neighborhoods with few recent sales. Keep a little cash in reserve and don't spend the "savings" before the appraisal clears.
The 30-year temptation, priced
Watch how seductive the wrong refinance looks. Take that same $320,000 balance and stretch it over a fresh 30 years at the same 6% the 20-year offer carries. The payment drops to $1,918.56 — a headline saving of over $500 a month against your current $2,428.46. It feels like winning. Now read the interest line: $370,682.20 across the new loan's life, against $321,113.09 if you simply stay where you are. The "saving" costs you $49,569.11 in extra interest, plus eight more years of payments than your current schedule asks for. Lower rate, lower payment, worse deal. That's not a paradox; it's the term doing exactly what terms do. Stretch any balance far enough and the monthly number turns painless while the total quietly eats a house deposit. Judge every refinance the way this calculator does: break-even first, lifetime interest second, payment last.
Rolling the closing costs into the loan
Lenders often offer to fold those $6,500 of closing costs into the new balance, so nothing comes out of your pocket. It sounds like a favor. Run it: the balance becomes $326,500, and at 6% over 20 years the payment is $2,339.15 instead of $2,292.58 — $46.57 more every month. The interest total climbs to $234,895.38, which is $4,676.33 more than paying the costs in cash. You haven't avoided the $6,500; you've borrowed it, at 6%, for twenty years. Sometimes that's still the right call — cash is tight, the break-even still works — but it should be a decision you make with the number on the table, not a default the loan officer slides past you. Paying the costs out of pocket also keeps the balance lower, which matters if you might sell or refinance again inside five years.
One procedural habit worth stealing: never compare refinances from phone quotes. Ask each lender for the official Loan Estimate — the standardized form where the rate, the closing costs and the cash-to-close sit in fixed boxes that can't hide. Two Loan Estimates side by side will tell you more in four minutes than a week of sales calls, because the form forces every fee into the open. If a lender stalls on producing one, that's your answer about the lender.
Do the same comparison honestly in the other direction too: before you refinance, pull your current loan's real remaining balance and remaining term from a recent statement, not from memory of the original loan. People routinely compare a shiny new offer against the loan they took out years ago instead of the one they actually hold today — and the loan you hold today, part-paid and part-aged, is the only honest baseline.
Frequently asked questions
How much should rates drop before refinancing is worth it?
The old rule says one percentage point, but the real test is your break-even: work out the monthly saving, divide the closing costs by it, and compare with how long you'll keep the loan. A 0.75% drop on a big balance you'll hold for 15 years can beat a 1.25% drop you'll sell out of in two.
What do closing costs on a refinance include?
Typically an application or origination fee, appraisal, title search and insurance, and various recording and underwriting charges — commonly 2–5% of the loan amount altogether. Always compare the full Loan Estimate documents, not the advertised rate.
What is a no-closing-cost refinance?
One where the lender covers the costs in exchange for a slightly higher rate. It isn't free — you're paying in interest instead of cash — but for a short expected stay it can actually be the cheaper structure, because the break-even starts at month one.
Does refinancing hurt my credit score?
Temporarily, a little: the application is a hard inquiry, and the new loan lowers your average account age. Both effects fade within months, and rate-shopping inquiries bunched within a short window usually count as one. The saving from a good refinance dwarfs the dip.
How soon can I refinance again?
There's no universal waiting period — some loan types impose one (often around six months of payments) — but each refinance restarts closing costs and the break-even clock. Serial refinancing every time rates wiggle usually enriches lenders, not borrowers.
Looking for more like this? Every calculator on CalcMega gets a plain-English guide with the formula and a worked example — browse them all on the CalcMega Blog.
Estimates only — actual offers, costs and eligibility depend on the lender. Nothing here is financial advice.