Mortgage Penalty Calculator
Find out what it costs to break your mortgage early, then see whether refinancing at a lower rate covers the penalty and when you break even.
⚠️ What is a Mortgage Penalty Calculator?
A mortgage penalty calculator estimates the cost of breaking a closed mortgage before the end of its term. When you signed your mortgage, you agreed to keep the loan until the term expires. Leaving early forces your lender to find a new borrower at current market rates, and if those rates are lower than yours, the lender loses interest income. The prepayment penalty compensates for that loss.
The most common reasons borrowers break a mortgage early include refinancing to take advantage of a significant rate drop, selling the home before the term expires, accessing home equity through a refinance, getting divorced and splitting assets, or blending and extending to a longer term at a lower rate. In each case, the penalty is the same: the greater of three months of interest or the interest rate differential (IRD).
Three months of interest is straightforward: it is exactly what its name says, the interest portion of three monthly mortgage payments calculated on your outstanding balance. The IRD is more complex. It measures how much extra interest your lender would have earned on your contract rate versus what they can earn by lending the same funds to a new borrower at today's rate for the same remaining period. When rates have fallen significantly, the IRD can dwarf the three-month interest amount and surprise borrowers who did not expect such a large penalty.
This calculator gives you both figures side by side and highlights the applicable penalty automatically. The Break-Even Analysis tab goes further: it calculates your monthly savings at the lower rate, divides the penalty by those savings to find the break-even month, and estimates your net five-year benefit. Use it to decide whether breaking now or waiting for your renewal date makes more financial sense for your specific situation.
📐 Formula
📖 How to Use This Calculator
Steps
💡 Example Calculations
Example 1 - Fixed-Rate Mortgage with Large IRD Penalty
$400,000 balance, 5.75% contract rate, 3.75% current rate, 48 months remaining
Example 2 - Variable-Rate Mortgage (3-Month Rule Only)
$280,000 balance, 6.20% variable rate, rates have risen so IRD does not apply
Example 3 - Break-Even Analysis for Refinancing Decision
$350,000 balance, 5.50% current rate, 4.00% new rate, 20-year remaining term, $15,750 penalty
❓ Frequently Asked Questions
🔗 Related Calculators
How is a mortgage prepayment penalty calculated?
Most fixed-rate mortgage penalties are the greater of 3 months of interest or the interest rate differential (IRD). The 3-month interest penalty equals your outstanding balance times your annual rate divided by 12, times 3. The IRD penalty equals the outstanding balance times the rate difference divided by 12, times the months remaining in your term. Your lender applies whichever is higher.
What is the interest rate differential (IRD) penalty?
The IRD penalty compensates the lender for the interest income lost when you break a fixed-rate mortgage early. It is calculated as: Balance times (Contract Rate minus Current Rate for your remaining term) divided by 12, times remaining months. If current rates are much lower than your contract rate, the IRD can be very large.
Is it worth breaking a mortgage to get a lower rate?
It depends on your break-even period. Divide the penalty by your monthly payment savings to find how many months until you recover the cost. If the break-even is less than your planned time in the home, refinancing is mathematically worthwhile. The Break-Even mode on this calculator does this math automatically.
How much is a typical mortgage penalty?
For a fixed-rate mortgage with 3 years remaining, the penalty is commonly 0.5 to 3 percent of the outstanding balance, depending on how much rates have moved since you took out the mortgage. On a $350,000 balance, that translates to $1,750 to $10,500. Apply the greater of the 3-month interest formula and the IRD formula to find your specific figure.
Can I reduce my mortgage penalty before breaking my mortgage?
Yes. Most mortgages allow an annual prepayment privilege of 10 to 20 percent of the original principal without penalty. Applying the full privilege before breaking the mortgage reduces the outstanding balance used in the penalty calculation. Some lenders also allow you to increase your regular payment. Both strategies can meaningfully reduce your penalty amount.
What is the 3-month interest penalty?
The 3-month interest penalty is the simplest prepayment penalty. It equals your outstanding balance times your annual interest rate divided by 12, times 3. This formula is always used for variable-rate mortgages and serves as the floor for fixed-rate mortgage penalties when the IRD would be lower.
Do variable-rate mortgages have prepayment penalties?
Variable-rate mortgages almost universally use only the 3-month interest penalty, with no IRD component. This makes them significantly cheaper to break than fixed-rate mortgages, especially when rates have fallen substantially since origination. The penalty on a $350,000 variable-rate mortgage at 6% would be approximately $5,250.
When does the IRD penalty exceed the 3-month interest penalty?
The IRD penalty exceeds the 3-month interest penalty whenever the rate difference times the remaining months is greater than 3. For example, if your contract rate is 5.5% and the current rate for your remaining term is 4.0%, the difference is 1.5%. At 36 remaining months, IRD equals 1.5/12 times 36 equals 4.5 months of interest, which is higher than the 3-month floor. The gap widens as rates fall further and as more time remains.
Can I avoid the penalty by porting my mortgage?
Yes. Porting transfers your existing mortgage rate and balance to a new property when you move, avoiding the penalty entirely. Not all mortgages are portable, and the new property must meet the lender's qualifying criteria. If your new home costs more than your current balance, most lenders let you blend and extend at a rate between your existing rate and the current market rate for the difference.
How does refinancing affect my amortization schedule?
When you refinance by breaking and renewing, your lender resets the amortization to the remaining term at the new rate. Your monthly payment drops because the rate is lower, but your total remaining payments stay the same in count. The net saving is the difference between what you would have paid in interest on the old schedule versus the new one, minus the penalty.
What happens if I break an open mortgage?
Open mortgages carry no prepayment penalty whatsoever. You can pay off the full balance at any time without cost. The tradeoff is that open mortgages carry higher interest rates than closed mortgages, typically 1 to 2 percentage points higher. They are designed for borrowers who expect to sell or pay off the loan within a few months.
How do I get the exact penalty from my lender?
Contact your lender directly and ask for a mortgage discharge statement or prepayment penalty quote. Lenders use slightly different versions of the IRD formula depending on whether they subtract from the posted rate or the actual contract rate. The figure in the discharge statement is binding, whereas this calculator gives you a reliable independent estimate using the standard industry methodology.