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
Penalty = max( 3-Month Interest, IRD )
3-Month Interest = Balance × (Annual Rate ÷ 12) × 3
IRD = Balance × (Contract Rate − Current Rate) ÷ 12 × Remaining Months
Balance = outstanding principal at the time of breaking
Annual Rate = your contract interest rate as a decimal
Contract Rate = interest rate agreed when you signed the mortgage (%)
Current Rate = lender's current rate for a term matching your remaining period (%)
Remaining Months = months left until your original term end date
Example: Balance $350,000, Contract Rate 5.5%, Current Rate 4.0%, 36 months remaining. 3-Month Interest = $350,000 × (0.055/12) × 3 = $4,813. IRD = $350,000 × (0.015/12) × 36 = $15,750. Penalty = max($4,813, $15,750) = $15,750.
📖 How to Use This Calculator
Steps
1
Select a mode - Choose Penalty Estimator to see what breaking your mortgage today would cost, or Break-Even Analysis to see whether refinancing is worth the penalty.
2
Enter your mortgage details - For Penalty Estimator: enter your outstanding balance, your current contract rate, the rate your lender currently offers for a term matching your remaining period, and the number of months left in your term.
3
Review the penalty breakdown - The calculator shows both the 3-month interest penalty and the IRD penalty, applies the higher of the two, and expresses your penalty as a percentage of the outstanding balance.
4
Run a break-even analysis - Switch to Break-Even Analysis, enter your balance, old rate, new rate you qualify for, remaining term in years, and the penalty amount. The calculator shows monthly savings, break-even months, and net savings over five years.
5
Model prepayment privileges - If your mortgage allows an annual prepayment, subtract that amount from your balance input to see how the privilege reduces your penalty before breaking.
💡 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
1
3-Month Interest = $400,000 × (0.0575 / 12) × 3 = $400,000 × 0.004792 × 3 = $5,750.
2
Rate difference = 5.75% − 3.75% = 2.00%. IRD = $400,000 × (0.02 / 12) × 48 = $400,000 × 0.001667 × 48 = $32,000.
3
Applicable penalty = max($5,750, $32,000) = $32,000. Penalty as % of balance = 8.0%.
Mortgage Penalty = $32,000 (IRD applies)
Try this example →Example 2 - Variable-Rate Mortgage (3-Month Rule Only)
$280,000 balance, 6.20% variable rate, rates have risen so IRD does not apply
1
Variable-rate mortgages use only the 3-month interest rule. 3-Month Interest = $280,000 × (0.062 / 12) × 3 = $280,000 × 0.005167 × 3 = $4,340.
2
Current rate for the remaining 18-month term is 6.50%, which is higher than 6.20%. IRD would be negative, so it does not apply.
3
Applicable penalty = $4,340. Penalty as % of balance = 1.55%. Variable-rate mortgages are inexpensive to break when rates have risen.
Mortgage Penalty = $4,340 (3-month interest)
Try this example →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
1
Original monthly payment at 5.50% for 20 years = $2,398. New monthly payment at 4.00% for 20 years = $2,121. Monthly savings = $277.
2
Break-even months = $15,750 / $277 = 57 months (4.7 years). This means you must stay in the home at least 57 months after refinancing to recover the penalty.
3
Net savings over 5 years = ($277 × 60 months) − $15,750 = $16,620 − $15,750 = $870. Over 10 years the net savings grow to $33,240 − $15,750 = $17,490.
Break-Even = 57 months | Net 5-yr savings: $870
Try this example →❓ Frequently Asked Questions
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, often exceeding $10,000 to $30,000 on a standard mortgage.
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 Analysis mode on this calculator does this math automatically for any combination of balance, rate, and penalty.
How much is a typical mortgage penalty?
For a fixed-rate mortgage with 3 years remaining, the penalty commonly ranges from 0.5 to 3 percent of the outstanding balance, depending on how much rates have moved since origination. On a $350,000 balance that means $1,750 to $10,500. When rates fall sharply the IRD can push the penalty to 4 to 8 percent of the balance, which is $14,000 to $28,000 on the same loan.
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. On a $350,000 balance with a 15% annual privilege, applying $52,500 first would reduce the penalty base to $297,500, cutting the IRD penalty proportionally.
What is the 3-month interest penalty?
The 3-month interest penalty equals your outstanding balance times your annual interest rate divided by 12, times 3. It is always used for variable-rate mortgages and serves as the floor for fixed-rate mortgage penalties. On a $350,000 balance at 5.5%, the 3-month penalty is $350,000 times 0.0055/12 times 3, which equals $4,813.
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. On a $350,000 variable-rate mortgage at 6%, the penalty is approximately $5,250, regardless of what current rates are doing.
When does the IRD penalty exceed the 3-month interest penalty?
The IRD exceeds the 3-month interest penalty whenever the rate difference times the remaining months is greater than 3. For example, at a 1.5% rate difference with 36 months remaining, IRD equals 1.5/12 times 36 equals 4.5 months of interest, which is higher than the 3-month floor. The gap widens further as rates fall and as more time remains on the term.
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, most lenders let you blend and extend at a rate between your existing rate and the current market rate for the additional amount.
How do I get the exact penalty figure from my lender?
Contact your lender directly and request a mortgage discharge statement or prepayment penalty quote. Lenders use slightly different versions of the IRD formula, particularly in whether they calculate from the posted rate or the actual discounted contract rate. The discharge statement is binding and legally accurate, while this calculator provides a reliable independent estimate using the standard industry methodology.
What happens if I break an open mortgage?
Open mortgages carry no prepayment penalty. You can pay off the full balance at any time without cost. The tradeoff is a higher interest rate, typically 1 to 2 percentage points above a closed mortgage. Open mortgages are designed for borrowers who expect to sell or pay off the loan within a few months and need the flexibility more than the lower rate.
Does breaking a mortgage affect my credit score?
Breaking a mortgage and refinancing with a new lender typically results in a hard credit inquiry, which may reduce your score by 5 to 10 points temporarily. Refinancing with your existing lender often involves a soft pull or no pull at all. The new mortgage appears as a new account on your credit file, which can temporarily lower the average age of accounts, but responsible repayment restores your score within 12 to 24 months.