"Should I refinance?" is one of the most googled money questions in America — and for good reason. Replacing your current mortgage with a new one at a lower rate can save tens of thousands of dollars over the life of the loan. But refinancing isn't free, and doing it at the wrong time can actually cost you money. This guide walks through the exact math, so you can answer the question with numbers instead of guesses.
What refinancing actually does
When you refinance, you take out a brand-new mortgage that pays off your existing one. The new loan has its own interest rate, its own term (15, 20, or 30 years), and its own closing costs. People typically refinance to:
- Lower the interest rate — the classic reason
- Shorten the term — e.g., from 30 to 15 years, to pay less interest overall
- Switch from adjustable to fixed rate — for payment stability
- Cash out equity — borrowing against the home's value (a different animal, with its own risks)
This article focuses on the first case: refinancing to save money.
The one number that matters: your break-even point
Refinancing costs money upfront — typically 2% to 5% of the loan amount in closing costs (origination fees, appraisal, title insurance, taxes). The break-even point tells you how many months of savings it takes to recover that cost:
Break-even (months) = Closing costs ÷ Monthly savings
If you'll keep the loan longer than the break-even period, refinancing wins. If you might sell or move before that, it loses.
A worked example
Say you have a $300,000 balance, 25 years remaining, at a 7.0% rate:
| Current loan (7.0%) | New loan (6.0%) | |
|---|---|---|
| Balance | $300,000 | $300,000 |
| Remaining term | 25 years | 25 years |
| Monthly payment (P&I) | $2,120 | $1,933 |
| Monthly savings | — | $187 |
With $9,000 in closing costs (3% of the balance):
Break-even = 9,000 ÷ 187 ≈ 48 months
You'd need to stay in the home about 4 years to come out ahead. Every month after that, the $187 is pure savings — over the remaining 21 years, roughly $47,000. You can reproduce this calculation with your own numbers using our financing calculator.
The rule of thumb — and when it fails
The old advice says refinancing makes sense when the new rate is at least 0.75 to 1 percentage point lower than your current one. It's a decent starting point, but it fails in two common situations:
- Small loan balances. On a $100,000 balance, a 1-point drop saves only ~$60/month. With $4,000 in closing costs, break-even takes over 5 years.
- Loans that are almost paid off. Late in a mortgage, most of your payment is principal, not interest. Refinancing restarts the amortization clock — you go back to paying mostly interest. If you're 20 years into a 30-year loan, even a lower rate can increase your total cost.
To see how much of each payment goes to interest versus principal at any point in your loan, check our guide comparison of amortization systems and the interest rate calculator.
Don't compare rates — compare APR
The advertised rate is not the whole story. Two lenders can offer the same 6.0% rate, but one charges $4,000 in fees and the other $9,000. The APR (Annual Percentage Rate) folds those costs into a single comparable number. When collecting quotes:
- Ask for the Loan Estimate — a standardized form every U.S. lender must provide
- Compare the APR line, not just the rate
- Watch for points: prepaid interest that lowers the rate but raises upfront cost
If a lender's numbers look suspiciously good, use our hidden interest rate calculator to reverse-engineer the real rate from the payment they quote.
Shortening the term: the aggressive strategy
If your budget allows, refinancing from a 30-year to a 15-year loan is where the big money is. Rates on 15-year mortgages are usually lower, and you cut the interest window in half. On $300,000:
| 30-year at 6.5% | 15-year at 5.9% | |
|---|---|---|
| Monthly payment | $1,896 | $2,516 |
| Total interest paid | ~$382,000 | ~$153,000 |
| Interest saved | — | ~$229,000 |
The payment rises by about $620/month — but the lifetime saving is enormous. Run your own scenario in the financing calculator before committing.
Checklist before you refinance
- Calculate your break-even point — costs divided by monthly savings.
- Be honest about how long you'll stay in the home.
- Check your credit score first — the best advertised rates assume excellent credit.
- Compare at least 3 Loan Estimates, using APR.
- Avoid extending your total timeline — if you're 5 years into a 30-year loan, consider a 25-year (or shorter) refinance so you don't add years of interest.
Bottom line
Refinancing is worth it when the math says so: a break-even point comfortably shorter than the time you'll keep the home, and a total interest saving that survives the reset of your amortization schedule. Ten minutes with a financing calculator can settle what rules of thumb only approximate.
Figures in this article are illustrative examples, not current market quotes, and don't constitute financial advice. Mortgage rates change constantly — always verify today's rates and total costs with lenders before deciding.