Estimate the prepayment penalty on a mortgage using three months’ interest or IRD.
Please do not make financial decisions based on these results.
What is the Mortgage Penalty Calculator?
Estimate the prepayment penalty on a mortgage using three months’ interest or IRD. To use the Mortgage Penalty Calculator, enter balance, your rate, current comparable rate, years left in term; it returns penalty (greater of the two), three months’ interest, interest rate differential, and shows them instantly as you type.
Understanding home financing
Buying or financing a home involves a handful of numbers that interact: the price, the down payment, the interest rate, the loan term and the ongoing costs of ownership. The mortgage calculator combines them into a monthly payment, while the amortization calculator shows how each payment is split between interest and principal.
Costs beyond the loan
Property taxes, homeowners insurance, mortgage insurance, association dues and maintenance all add to the monthly cost of owning. Lenders also look at your debt-to-income ratio and your savings, so check what you can afford with the house affordability calculator before you start house hunting.
Changing the loan later
Once you own, you may want to lower the rate, shorten the term or borrow against your equity. The refinance calculator and the mortgage payoff calculator help you compare those choices with the loan you already have.
How to use the Mortgage Penalty Calculator
- Fill in the fields. You will need Balance ($), Your rate (%), Current comparable rate (%), Years left in term. Use figures from a lender quote or your tax bill where you have them, and keep the term and rate realistic. Fields marked optional can stay at zero.
- Read the result. The highlighted box gives the Penalty (greater of the two), and the cards below show Three months’ interest, Interest rate differential. Tables and charts break it down further.
- Test other scenarios. Results update as you type. Change one value at a time to see what drives the answer, and press Reset to go back to the defaults.
Formula and how it works
Example with real numbers
Here is the Mortgage Penalty Calculator using the default values shown in the calculator above:
Inputs
| Balance ($) | 300,000 |
|---|---|
| Your rate (%) | 5.5 |
| Current comparable rate (%) | 4.5 |
| Years left in term | 3 |
Results
| Penalty (greater of the two) | $9,000.00 |
|---|---|
| Three months’ interest | $4,125.00 |
| Interest rate differential | $9,000.00 |
With these inputs the calculator returns Penalty (greater of the two): $9,000.00. Change any value in the calculator to see how the result moves.
What if you change one input?
Sensitivity check: raising Balance ($) from 300,000 to 360,000 (about 20% higher) and leaving everything else as in the example above changes the results like this:
| Result | Example | After the change | Change |
|---|---|---|---|
| Penalty (greater of the two) | $9,000.00 | $10,800.00 | +20% |
| Three months’ interest | $4,125.00 | $4,950.00 | +20% |
| Interest rate differential | $9,000.00 | $10,800.00 | +20% |
The input that moves the result most is the one to check twice. Change it in the calculator above to test your own case.
What the results tell you
The results panel of the Mortgage Penalty Calculator reports Penalty (greater of the two), three months’ interest and interest rate differential. Compare these figures while changing one input at a time, and use the related calculators below to look at the same situation from another angle.
Method and limits. This calculator applies the formula in the section above to your inputs, in your browser; nothing you enter is stored on our servers. The result is only as accurate as the numbers you enter and the formula shown above. It is for information, not financial, tax or legal advice.
Frequently asked questions
How is the penalty chosen?
Lenders charge the greater of three months’ interest or the interest rate differential.
What is included in a monthly mortgage payment?
Principal and interest, plus property tax, homeowners insurance, PMI if your down payment is under 20%, and HOA fees if they apply.
How much house can I afford?
A common rule is to keep housing costs under about 28% of gross income and total debt under 36%. The House Affordability Calculator applies those limits to your numbers.
Are the results guaranteed?
No. Results depend entirely on the numbers you enter and the formulas shown on this page. Please do not make financial decisions based on them alone; confirm important figures with a licensed professional.
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