Current Monthly Payment
New Monthly Payment
Monthly Savings
Break-Even on Closing Costs
Lifetime Interest Savings
Table of Contents
Monthly Savings, Break-Even & Lifetime Cost
A lower rate alone doesn't mean a refinance saves money — closing costs and the new term reset the math. This calculator gives you the three numbers that actually matter: monthly savings, the month you break even on closing costs, and the lifetime interest difference after costs.
How the refinance numbers are calculated
The calculator runs the standard amortization formula twice — once for the current loan, once for the new loan — and compares the results.
M = P × [ r(1+r)n ] ÷ [ (1+r)n − 1 ]
- M — monthly principal-and-interest payment
- P — loan balance
- r — monthly interest rate (annual rate ÷ 12)
- n — remaining (or new) number of monthly payments
The break-even point and lifetime savings are then:
Break-even (months) = Closing costs ÷ Monthly savings
Lifetime savings = Current total interest − New total interest − Closing costs
Worked example using the calculator's defaults ($280,000 balance, current loan: 7.0% with 27 years remaining; new loan: 5.5% over 30 years; $6,000 closing costs):
- Current payment: $280,000 × (0.005833 × (1.005833)324) ÷ ((1.005833)324 − 1) ≈ $1,914.96/month
- New payment: $280,000 × (0.004583 × (1.004583)360) ÷ ((1.004583)360 − 1) ≈ $1,590.10/month
- Monthly savings = $1,914.96 − $1,590.10 ≈ $324.86
- Break-even = $6,000 ÷ $324.86 ≈ 18.5 months
- Current total interest over 27 yrs ≈ $340,247; new total interest over 30 yrs ≈ $292,435
- Lifetime savings ≈ $340,247 − $292,435 − $6,000 ≈ $41,812
Two things to notice: the new loan adds 3 years to the timeline (this is the "clock reset" effect), but the rate drop is large enough that the borrower still comes out ahead in lifetime cost. With a smaller rate drop, the clock reset alone could eat the savings entirely.
When the rate drop is enough
On a $280,000 balance with 27 years remaining and $6,000 closing costs, refinancing into a fresh 30-year loan:
| Current rate | New rate | Monthly savings | Break-even | Lifetime savings* |
|---|---|---|---|---|
| 7.0% | 6.5% | $144 | 42 months | About $6,400 |
| 7.0% | 6.0% | $236 | 26 months | About $25,000 |
| 7.0% | 5.5% | $325 | 19 months | About $42,000 |
| 7.0% | 5.0% | $411 | 15 months | About $58,000 |
*Lifetime savings include the 3-year clock-reset penalty when refinancing from a 27-year remaining term into a new 30-year. A 0.5% drop barely covers closing costs over the loan life — that's why traditional advice was to wait for at least a 1% rate drop. A 1.5%+ drop produces meaningful savings even with the longer term.
Cash-out vs rate-and-term refinance
Two distinct products, both called refinancing:
- Rate-and-term refinance — loan amount stays the same, rate or term (or both) change. The simplest case and what this calculator models. Lowest rates, fewer underwriting hurdles.
- Cash-out refinance — new loan is larger than the old loan; the difference is paid to you in cash, typically used for home improvements, debt consolidation, or large expenses. Rates are usually 0.125–0.5% higher than rate-and-term refinances, and lenders cap cash-out LTV at 80% for most conventional loans.
If you need cash but your existing first-mortgage rate is already low (e.g., a 3% loan from 2021), a HELOC or home equity loan is usually a better choice than a cash-out refinance — you keep the cheap first lien intact.
The clock-reset trap
Resetting amortization is the most commonly missed cost of refinancing. A borrower 10 years into a 30-year loan has roughly 20 years remaining; refinancing into a fresh 30-year adds those 10 years back to the payoff timeline. Even at a lower rate, the extended term can produce more total interest paid.
Three ways to avoid the trap:
- Refinance into a matching term. If you have 23 years remaining, ask for a 20- or 23-year refinance. Most lenders offer non-standard terms on request.
- Refinance into a shorter term. 30-to-15 refinances usually capture an additional 0.5–0.75% rate discount and compress total interest dramatically — if the higher monthly payment fits your budget.
- Keep the 30-year, pay extra. Take the lower payment but apply the monthly savings as additional principal. You get the rate benefit without the term extension.
What's in refinance closing costs
Refinance closing costs typically run 2–5% of the loan amount. On a $280,000 refinance, expect $5,600–$14,000. The main line items:
- Loan origination fee — 0.5–1% of the loan amount, the lender's primary charge.
- Appraisal — $400–$800 typical.
- Title insurance and search — $500–$2,000 depending on state and loan size.
- Recording fees and transfer taxes — vary heavily by state; some states impose no transfer tax on refinances, others charge significant amounts.
- Prepaid items — escrow funding for property taxes and homeowners insurance, plus prepaid interest from closing to month-end.
- Credit report, flood certification, attorney fees — smaller line items in the $50–$1,000 range.
Always request a Loan Estimate (the standardized CFPB disclosure form) from at least three lenders — comparing them line-by-line often reveals $1,000–$3,000 in negotiable charges.
Limitations of this calculator
- Assumes the same loan balance for both old and new loans. A cash-out refinance with a higher balance produces different numbers; rerun with the new total balance.
- Models principal and interest only. Property taxes, insurance, and PMI continue separately and don't change with a rate-and-term refinance.
- Does not factor in any prepayment penalty on the existing loan (rare on owner-occupied mortgages but possible on older or non-conforming loans).
- Lifetime savings calculation assumes you keep the new loan to maturity. If you refinance or sell before maturity, the actual savings are lower.
Sources & references
- Consumer Financial Protection Bureau — Refinancing — refinance process, disclosures, and the standardized Loan Estimate form.
- Freddie Mac Primary Mortgage Market Survey — weekly tracking of average US mortgage rates by product, useful for assessing whether current rates justify refinancing.
- Federal Reserve Finance and Economics Discussion Series — research on the refinancing decision and borrower outcomes.
FAQs
Break-even is the number of months your monthly savings must accumulate to recoup the closing costs. On a $6,000 closing cost with $250/month savings, break-even is 24 months. Below the break-even, refinancing loses money even at a lower rate; above it, you save. The rate alone tells you nothing about whether the trade is worthwhile — the right question is how long will you keep this loan, measured against the break-even month.
The old rule of thumb is 1%, but it depends on loan size and how long you'll keep the loan. On a $100,000 balance, a 0.5% drop saves about $30/month — closing costs of $3,000 take 100 months to recoup. On a $500,000 balance, the same 0.5% drop saves $150/month and recoups in under 2 years. Always run the break-even math for your specific numbers rather than relying on a generic threshold.
Paying up front is mathematically cheaper because you avoid paying interest on the closing costs for the life of the loan. But it requires having the cash available and getting nothing back if you sell or refinance again before break-even. Rolling costs into the loan or accepting a no-closing-cost refinance (where the lender covers fees in exchange for a slightly higher rate, typically +0.25%) trades total cost for cash-flow flexibility. Compare break-even both ways before deciding.
It can — but resetting the clock can cost more in total interest than it saves in rate. If you're 7 years into a 30-year mortgage and refinance into a new 30-year at a lower rate, you've added 7 years of interest payments to your timeline. The fix is either to refinance into a 23-year loan instead (most lenders accommodate non-standard terms on request) or to keep the new 30-year but apply the monthly savings as extra principal to hold your original payoff date.
Skip the refinance if you'll move or refinance again before break-even, if your current rate is already at or below current market rates, if your credit has gotten worse since the original loan (you may not qualify for a better rate), if you have less than 20% equity (PMI requirements may erase savings), or if you're more than halfway through the original term — resetting amortization on a nearly-paid-off loan rarely pays off because most of your remaining payments are already principal.