What Your Low-Rate Mortgage Is Worth: The Lock-In Math Behind 'Should We Move?'
Millions of homeowners feel stuck with a mortgage rate they'll never see again. Here is how to put an actual dollar value on that rate, and how to decide whether a move is still worth it.
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📐 Figures verified Sep 28, 2026 against Freddie Mac's Primary Mortgage Market Survey (the September 2026 average of weekly 30-year rates, about 6.86%), IRS Publication 523 on selling a home, the CFPB's Owning a Home resources and HUD's home-buying guidance. The worked example is computed from standard loan formulas. This is general information, not financial advice. How we check numbers →
A low-rate mortgage is an asset. With $300,000 left at 3% and new 30-year loans near 6.9%, it's worth about $96,147: the gap between your balance and what your remaining payments are worth at today's rates. Moving means giving that up and paying about $545 more a month on the same loan amount. Weigh that against what the move is worth to you.
Numbers That Matter
| Figure | Amount | Source | Verified |
|---|---|---|---|
| 30-year fixed mortgage rate, September 2026 average | About 6.86% | Freddie Mac PMMS | Sep 28, 2026 |
| Home-sale gain exclusion | $250,000 ($500,000 joint) if ownership and use tests are met | IRS Publication 523 | Sep 28, 2026 |
| Comparing a new loan | Loan Estimates and closing-cost tools | CFPB | Sep 28, 2026 |
| Buying-process guidance | Buyer programs and counseling | HUD | Sep 28, 2026 |
How to Value Your Low Rate
Your mortgage's worth is the difference between what you owe and the present value of your remaining payments at today's rate. When market rates are far above yours, those payments are cheap money, and the gap can be tens of thousands of dollars. It's the same math a lender uses: a bank would happily pay you to take back a 3% loan when it can lend at 6.9%.
The Should-We-Move Math, Step by Step
- Find your lock-in value: balance minus the present value of your remaining payments at today's rate.
- Price the payment jump: what the same loan amount costs at today's rate, and what your new loan amount will be.
- Add transaction costs: selling and buying costs, moving and any repairs, which often total several percent of the home's price.
- Put a value on the reasons to move: a job, schools, space, a shorter commute or being near family.
- Check alternatives: an assumable loan on the next home, renting out your current one, or renovating with a home-equity line instead of moving.
Worked Example: A 3% Loan vs Today's Rates
- Today: the 3% loan costs $1,423 a month in principal and interest.
- Replacing it: the same $300,000 on a new 30-year loan at 6.86% costs $1,968, or $545 more a month ($6,542 a year).
- The lock-in value: at 6.86%, the remaining payments are worth $203,853, so the loan is worth about $96,147 to you.
- If rates fall to 5.5%: that value shrinks to about $68,334, which makes moving cheaper.
Principal and interest only; taxes, insurance and transaction costs come on top.
Decision Rules
If this, then that
- If the move pays for itself (a raise, lower living costs) → the lock-in value is a cost to weigh, not a veto.
- If you're moving for more space only → price a renovation or addition against the payment jump.
- If your next home has an assumable FHA or VA loan → you may keep a lower rate on the new place.
- If you'd keep the current home as a rental → run landlord math, including the tax rules on a later sale.
- If rates fall → recalculate; the value of your old loan drops as market rates come down.
Mistakes to avoid
- Staying put for the rate alone when the move would clearly improve your life or income.
- Comparing only monthly payments and ignoring transaction costs.
- Forgetting the home-sale tax exclusion rules if you convert to a rental.
- Assuming you can take your old rate with you; U.S. mortgages generally aren't portable.
- Waiting indefinitely for rates to drop.
Related: how to refinance covers when a new loan pays; closing costs explained covers transaction costs; assumable mortgages covers taking over a low-rate loan; and rate-hike cycles since 1980 shows how mortgage rates have moved.