Loan Portability Calculator — How Much Can You Save by Switching Lenders?
Transfer your mortgage to a lender offering a lower rate and see the monthly savings, total savings and how long it takes to recover the fees.
Results
Loan Balance: Current vs. New Rate
Monthly Payment: Current vs. New Rate
Compare Scenarios
Save different rate offers and fees, then view them side by side.
What Is Mortgage Portability and When Does It Pay Off?
Mortgage portability lets you transfer your outstanding balance from your current lender to another lender offering a lower interest rate. Because you keep the same balance and remaining term, every month at the lower rate reduces your interest cost. Portability pays off when the monthly savings quickly cover the fees charged to switch.
How to Read Your Payback Period
The payback period is the number of months it takes for your monthly savings to cover the portability costs. Divide the total fees (TAC, appraisal, notary, registration) by the monthly savings. After the break-even month, every month of savings is money in your pocket for the rest of the loan term.
How Your Portability Savings Are Calculated
The portability calculator compares two amortized loans with the same outstanding balance and remaining term: your current loan at your current rate, and the new loan at the rate your new lender is offering. For each one, it uses the standard amortization formula to find the principal-and-interest payment and the total interest over the remaining term.
The monthly saving is simply the difference between the two payments. The calculator multiplies that saving across every remaining month to get your total savings and total interest saved, then subtracts the portability costs (loan opening fee, appraisal, notary and registration) to show your net benefit. Finally, it divides the total costs by the monthly saving to find the payback period — the number of months before the switch pays for itself.
Worked Example: $250,000 at 9% Moving to 7%
Say you have $250,000 outstanding on a 30-year mortgage at 9%, and a new lender offers you 7% for the same remaining term. Your current monthly payment is about $2,011. The new payment at 7% is roughly $1,663 — a saving of about $348 per month.
If the portability costs total $2,500, divide that by the $348 monthly saving: you break even in a little over 7 months. Over the remaining term, the total savings reach roughly $125,000 in interest — far more than the fees. If you keep the mortgage for at least a couple of years, portability is almost certainly worth it.
Frequently Asked Questions
What is mortgage portability?
Mortgage portability lets you transfer your existing loan balance from your current lender to a new lender offering a lower interest rate, without paying off the loan in full. You keep the same outstanding balance and remaining term.
How is the payback period of a portability calculated?
Divide the total portability costs (TAC, appraisal, notary, registration) by your monthly savings. If you save $150 a month and the costs are $1,800, you break even in 12 months. Every month after that is pure savings.
When does loan portability not make sense?
Portability usually does not pay off when the new rate is not meaningfully lower, when the remaining term is very short, or when the fees are high compared with the monthly savings. Run the numbers here before switching.
What does a mortgage portability calculator show?
A mortgage portability calculator shows your current and new monthly payments, the monthly saving from switching, the total saved over the remaining term, how much interest you avoid, and how many months it takes to recover the portability fees. It answers the key question: does switching lenders pay for itself before you would otherwise pay off or refinance?
Can I make 13 payments a year on my mortgage?
Yes. Paying every two weeks — half the monthly payment 26 times a year — works out to 13 full payments a year instead of 12. The extra payment goes straight to principal, cutting years off the term and saving interest. This works on top of portability: switch to a lower rate first, then add the extra payment to maximize the total interest saved.
Does portability require a new appraisal or credit check?
Usually yes. The new lender assesses your credit again and, depending on the lender and your loan-to-value ratio, may ask for a property appraisal. That is why the costs estimate in the calculator includes an appraisal fee — remember to factor it in, since it delays your payback period.