The old “refinance if you can drop 1%” rule is folklore. It ignores balance, closing costs and how long you will stay — all of which matter more than the rate change itself.
The actual calculation
- Current principal and interest payment
- New principal and interest at the proposed rate and term
- Monthly saving = the difference
- Total closing costs
- Break-even months = closing costs ÷ monthly saving
If break-even lands before you expect to sell or refinance again, proceed.
Why the 1% rule fails
Large balance: $700,000 at 7.0% → 6.5%. Saving $232/month. Costs $9,000. Break-even 39 months. Worth it despite only half a point.
Small balance: $150,000 at 7.0% → 5.75%. Saving $117/month. Costs $5,500. Break-even 47 months — despite a 1.25% drop.
Same rule, opposite conclusions. Balance drives the saving; costs are relatively fixed.
The term-reset trap
The most expensive mistake in refinancing.
You are eight years into a 30-year loan at 7%, balance $340,000, payment $2,528, with 22 years left.
You refinance into a new 30-year at 6% and the payment drops to $2,038 — a saving of $490 a month. Excellent, apparently.
But you have added eight years back. Remaining interest on the old loan was about $327,300. On the new loan it is about $393,850.
You lowered the payment and raised lifetime interest by roughly $66,500.
The fix: refinance into a term matching your remaining one — a 20-year here. Payment about $2,436, still saving $92 a month, and total interest drops to about $244,600, roughly $82,700 less than staying put.
If cash flow is the goal, the 30-year is defensible. If total cost is the goal, it is not. Know which you are optimising for.
Beyond rate
Refinancing can be right even without a lower rate:
- Removing mortgage insurance — refinancing FHA into conventional at 20% equity can save more than a rate change would
- ARM to fixed before an adjustment
- Removing a co-borrower after divorce
- Shortening the term deliberately
- Consolidating a second lien
“No-cost” refinances
Costs are covered by lender credits in exchange for a higher rate, or rolled into the balance. Neither is free.
They can still be correct — particularly if you expect to refinance again soon, since there is no upfront cost to recover. Run the same break-even against the higher-rate version and compare.
The refinance calculator gives you the break-even month and a plain verdict.
Common questions
There is no universal threshold. What matters is whether the monthly saving recovers the closing costs before you sell or refinance again.
The costs are paid through a higher rate or added to the balance. Nothing is free — but it can still be the right structure.
General information, not advice on your specific situation. Guidelines, limits and pricing change, and vary by lender, programme and state. Nothing here is a commitment to lend or an offer of credit. For tax or legal questions, consult a qualified professional.
Sree Basireddy · Mortgage Loan Officer, NMLS 2705737 · Loan Factory, Inc., NMLS 320841 · Equal Housing Opportunity