The five-minute test that tells you if a refi makes sense

Refinancing a loan — a mortgage, a car loan, a student loan — almost always involves closing costs, paperwork, and a credit pull. Whether all of that is worth it comes down to one ratio: how long does it take for the lower payment to pay back the fees you spent to get it?

That number has a name: the break-even period. It's the only calculation you need to decide whether to keep going. This is how to estimate it in about five minutes — and the rules of thumb for when the answer is obvious before you finish the math.

The three numbers you need

1. Your current monthly payment on the loan you're considering refinancing.
2. The new monthly payment at the rate you've been quoted. Most lenders will give you this number in a soft-pull pre-qualification.
3. Total closing costs on the new loan. For mortgages this is the loan estimate disclosure (origination, appraisal, title, recording, points). For student loans and auto loans, it's usually zero or a small origination fee.

The calculation

Break-even period (in months) = closing costs ÷ monthly payment savings.

That's it. If your current payment is $2,400, your new payment is $2,200, and your closing costs total $4,000, the math is $4,000 ÷ $200 = 20 months. That's how long the lower payment has to be running before you've recouped the fees.

The decision rules

Once you have the break-even, three questions decide it:

1. Are you going to be in this loan for at least the break-even period? If you're planning to sell the house in 18 months and the break-even is 24 months, the math says no — you'd pay the closing costs and move before they paid you back.
2. Is the break-even period a small fraction of the loan's remaining life? A 20-month break-even on a 28-year-remaining mortgage is excellent. A 20-month break-even on a 30-month-remaining car loan is barely worth the paperwork.
3. Are you actually getting a lower total cost, not just a lower monthly payment? Stretching a loan's remaining term lowers the monthly payment but can raise the total interest paid. This is the part that gets people in trouble.

The trap: lower payment, more interest

A $250,000 mortgage with 20 years left at 6.5% has a monthly payment of about $1,864 and total remaining interest of about $197,000. Refinance that into a new 30-year mortgage at 5.5% and the monthly payment drops to about $1,420 — a savings of $444/month, which feels great. But the total interest over 30 years is about $261,000. You saved $5,300/year in cash flow and added $64,000 in lifetime interest.

The fix isn't to skip refinancing — it's to refinance into a term that matches your original payoff date. A 20-year refi at 5.5% on the same $250,000 has a monthly payment of about $1,720 (still $144/month less than the current one) and total interest of about $163,000 — $34,000 better than the no-refi baseline.

Most lenders will quote you the 30-year by default because it's the loosest payment they can offer. Ask for the term that matches your current payoff date and compare those two.

The two-rate rule for mortgages

The classic rule of thumb is: refinance if you can drop your rate by at least 0.75 to 1 percentage point. It's a useful guardrail because it usually means the break-even comes in under 36 months, which is short enough that most homeowners are still in the house. But it's not a hard rule — the break-even math above is the actual answer.

Where the rule of thumb fails:

• Very low loan balances (under ~$150K) — closing costs are similar regardless of loan size, so a 1-point rate drop on $100K saves less per month and pushes the break-even out further.
• Very large loan balances — even a 0.4-point drop on a $700K mortgage saves enough per month to break even fast.
• Rate-and-term refis vs. cash-out refis — closing costs run higher on cash-out, and you're increasing the loan balance, which changes the math entirely.

Student loans and auto loans

Student loan refis usually have zero closing costs. The break-even period is effectively zero, which makes the only question whether the new rate is actually lower than the old one and whether you're giving up federal protections (income-driven repayment, deferment, forgiveness eligibility) by moving from federal to private. The math is easy; the tradeoff is the harder question.

Auto loan refis also generally have small fees, and most car loans are short enough that the break-even is fast if the rate drop is meaningful. The wrinkle is that older cars (5+ years) often can't be refinanced at all — many lenders cap collateral age.

When to skip the test entirely

• Your current rate is at or below current market rates. A refi can't help you here.
• You're planning to sell or pay off the loan within 12 months. Break-even almost always loses.
• The new loan extends your payoff date by more than ~5 years and you can't commit to paying it down faster than the new schedule.

How to run your own numbers

Once you have a quote in hand, the Debt Clocktool above will show you the payoff timeline and total interest on both the current loan and the proposed new loan. Run it twice — once with your current rate and balance, once with the new rate and the term you're actually planning to use. The difference in the “total interest” line is the part the break-even calculation doesn't show you.

What this five-minute test doesn't cover

• Cash-out refinancing changes both the loan balance and the use of funds. The break-even math still works, but you also need to decide whether trading equity for cash is the right move — a separate question.
• Mortgage points. Paying points to buy down the rate is its own break-even calculation (cost of points ÷ monthly savings from the lower rate). The same shape of math, applied earlier in the process.
• Tax effects. Mortgage interest is deductible only if you itemize, and most filers don't. If you do, lower interest payments mean a slightly smaller deduction — usually a small effect, but worth being aware of.

For why even small payment differences compound, see what one extra payment can change.

Once the five-minute test says “run the real numbers,” the Refi Break-Even tool takes your specific loan, the rate quote, the closing costs, and how long you plan to stay — and returns the actual break-even months, the honest total-cost crossover, and a structural read on whether the move pays back before you move.