Mortgage Refinance Calculator — Break-Even & Savings

What this Mortgage Refinance Calculator does

This English-language mortgage refinance calculator gives you a side-by-side comparison of your existing loan and a potential refi — new monthly payment, monthly savings, break-even point in months, and total lifetime interest saved or lost. Most refi estimators stop at the lower payment and call it a win. This tool surfaces the break-even month alongside closing costs so you can answer the only question that matters: will I stay in the home long enough for the savings to exceed what I paid to refinance? A homeowner in Austin dropping from 7% to 5.5% on a $400,000 balance might save $390/month but carry $8,000 in closing costs — the break-even is month 21, and if you're planning to move in two years, the refi costs you money. The calculator handles that math instantly. 100% client-side — your data never leaves your browser. No uploads, no tracking, no server logs. If you want to model how savings compound over time, pair this with our [compound interest calculator](/en/compound-interest-calculator/).

Features

Break-even month. Divides your total closing costs by your monthly savings to show exactly how many months until refinancing pays for itself — critical if you're not planning to stay long-term.
Lifetime interest comparison. Calculates total interest paid on both the current and new loan over their full remaining terms, so you can see whether a lower rate with a reset 30-year clock actually saves money.
Go / no-go recommendation. Flags the 'depends on how long you stay' scenario explicitly. If break-even exceeds a typical move horizon, the tool calls it out rather than defaulting to an optimistic recommendation.
Cash-out refi support. Accepts a new principal larger than your current balance to model cash-out refinancing. Useful for comparing a straight rate-and-term refi against pulling equity for home improvements.
Adjustable term comparison. Model a 30-to-15-year term shortening. You'll see the higher monthly payment alongside the dramatic reduction in lifetime interest — a common scenario when rates drop and income has grown.
No registration, no PII. All arithmetic runs in your browser using standard floating-point math. Nothing is transmitted. You can audit the computation offline and get consistent results every time.

How to use the Mortgage Refinance Calculator

Fill in your current loan details and the proposed new loan details, then click Calculate to see the full comparison.

Enter your current mortgage. Input your remaining balance, current interest rate, and months remaining. Example: $320,000 balance, 7.25% rate, 312 months left.
Enter the new loan terms. Input the proposed rate, new term in months, and new principal (same as current balance for rate-and-term; higher for cash-out). Example: 5.5% rate, 360 months, $320,000.
Add closing costs. Enter estimated closing costs in dollars. Typical U.S. closing costs run 2–5% of the loan amount. This is what the break-even calculation divides against your monthly savings.
Review the results. The output shows new monthly payment, monthly savings, break-even month, lifetime interest for each loan, and a plain-English recommendation. Use the Copy button to save results.
Stress-test multiple scenarios. Change the rate by 0.25% increments or adjust the term to compare a 20-year vs 30-year refi. Run the tool several times before talking to a lender — it's free and instant.

Common use cases

Rate-and-term refi decision. You locked in at 7% in 2023 and rates have dropped to 5.5%. Plug in your balance, both rates, and closing costs to find your break-even month and decide whether now is the right time to refinance.
Cash-out refinance comparison. Considering pulling $40,000 in equity for a renovation? Use the cash-out refi calculator mode to compare your current payment against the new, larger loan and see the true cost of that equity over the loan term.
Shortening your loan term. A Boston homeowner five years into a 30-year mortgage may want to refinance into a 15-year loan. This calculator shows how much the monthly payment rises and how many years of interest you eliminate — a trade-off most refi estimators understate.
Pre-lender stress testing. Run four or five refi scenarios — different rates, terms, and closing cost estimates — before sitting down with a lender. You'll negotiate from a clearer position and spot aggressive assumptions faster. For a broader picture of total loan cost, our [loan calculator](/en/loan-calculator/) covers amortization from scratch.
Student loan impact on refi eligibility. High student debt raises your debt-to-income ratio and can limit what rate you qualify for. Model the refi math at a slightly higher rate than advertised to stress-test whether the break-even still works.

Frequently asked questions

Is my financial data stored or shared anywhere?

No. Every calculation runs entirely in your browser. No data is sent to any server, logged, or shared with third parties. You can disconnect from the internet and the calculator still works. This is what '100% client-side' means in practice — unlike most financial tools, there is no back-end processing your loan figures.

What is a break-even point and why does it matter?

The break-even point is the month at which your cumulative monthly savings equal your upfront closing costs. Before that month, you've spent more on closing costs than you've saved. After it, you're in the black. If you plan to sell or move before the break-even month, refinancing costs you money regardless of the lower rate — this is the scenario most mortgage refinance estimators gloss over.

How do I estimate closing costs for a refi?

U.S. closing costs for a refinance typically run 2–5% of the loan balance, covering origination fees, appraisal, title insurance, and prepaid items. For a $300,000 loan, budget $6,000–$15,000 as a starting range. Your lender is required to provide a Loan Estimate within three business days of application — use that figure once you have it, and re-run this refi calculator to confirm the break-even still makes sense. You can reference NIST SP 800-63B guidance if you're also evaluating lender identity verification practices.

Does refinancing into a lower monthly payment always save money?

Not necessarily. If you restart a 30-year clock on a loan you've been paying for 10 years, you're adding 10 years of interest even if the rate is lower. This calculator shows total lifetime interest for both scenarios side by side, so you can see when a lower payment actually costs more over the full term — a pitfall that catches many first-time refinancers.

What's the difference between a refi estimator and this calculator?

Many online refi estimators show only the new payment and advertised monthly savings. This mortgage refinance calculator also computes the break-even month against closing costs and total lifetime interest paid on both loans — the two numbers that determine whether refinancing is actually worth it for your specific situation.

How accurate are the results?

Results are mathematically precise for fixed-rate loans using standard amortization formulas — the same math your lender uses. Floating-point arithmetic in browsers follows MDN — crypto.randomUUID — actually, for financial math, IEEE 754 double-precision is the standard, and rounding is applied to two decimal places to match real-world statements. Variable-rate mortgages, PMI, escrow changes, and tax implications are outside scope — treat results as a planning baseline, not a lender quote.