What Actually Happens When You Refinance a Mortgage
Published 2026-07-26 · 3 min read · By Supabus
"Should I refinance?" usually gets answered with a gut feeling about interest rates. The actual answer depends on three numbers most people never calculate: the new monthly payment, how long it takes the savings to cover the closing costs, and what happens over the full remaining life of the loan.
The monthly payment comparison
This part is straightforward: take your current loan's remaining balance, rate, and remaining term, and compare the payment against a new loan at the new rate and term. A lower rate doesn't automatically mean a lower payment, either - stretching the term back out to a fresh 30 years can lower the payment even at a similar rate, while a shorter new term can raise it even at a better rate.
The break-even point
Refinancing isn't free - there are closing costs. The break-even point is simply:
break-even (months) = closing costs ÷ monthly savings
Rounded up to the next whole month. If your new payment is $150/month lower and closing costs are $3,000, you break even in 20 months - after that, the lower payment is genuinely money back in your pocket. If you're planning to move or refinance again before that point, the new loan may not be worth it despite the lower rate.
If the new payment isn't actually lower than the old one, there's no break-even point to calculate at all - refinancing at that point would need a different justification (e.g. switching from an adjustable to a fixed rate) than pure monthly savings.
The full-lifetime comparison
Monthly savings and break-even are useful, but they don't capture everything - a longer new term can look great on a monthly basis while costing more in total interest over the life of the loan. The fuller picture compares the total interest you'd pay if you kept your current loan for its remaining term against the total interest on the new loan over its own term, minus the closing costs.
One honest caveat: if the new loan's term is a different length than your current loan's remaining term, this isn't a perfectly apples-to-apples comparison - but it's the standard way most refinance calculators frame the decision, and it's still far more informative than comparing interest rates alone.
What this kind of estimate leaves out
A principal-and-interest calculation - the kind any refinance calculator does - doesn't include property taxes, homeowners insurance, or PMI. Those can change with a new loan too (particularly PMI, which depends on your new loan-to-value ratio), and they don't show up in a P&I-only monthly payment comparison. Worth checking separately before treating any calculator's number as the final word.
Try it yourself
Our Mortgage Refinance Calculator runs all three of these numbers - new payment, break-even, and net lifetime savings - from your current loan details and a refinance offer, instantly.