A mortgage payment tells you how much you pay each month, but it doesn’t show how quickly you are actually paying off your home loan. A mortgage amortization schedule breaks each payment into principal and interest, tracks the balance you still owe, and shows how the loan progresses toward being paid off.
Use this mortgage amortization calculator to examine your monthly payments, estimate total interest over the life of your loan, and see how additional principal payments could shorten your repayment timeline. Enter your mortgage amount, annual interest rate, loan term, and any extra monthly principal payment to compare different repayment scenarios.
What Your Mortgage Amortization Schedule Reveals
An amortization schedule is a payment-by-payment record of how your mortgage balance changes. Each row shows what happens when you make a scheduled payment, making it easier to see where your money goes and how much of the loan remains unpaid.
A typical schedule includes:
- Beginning balance: The principal you owe before the payment is applied.
- Scheduled payment: The regular amount allocated to principal and interest.
- Interest paid: The borrowing cost calculated for that payment period.
- Principal paid: The portion that reduces the amount you borrowed.
- Ending balance: The principal remaining after the payment.
- Cumulative interest: The interest charged up to that point, if shown in the results.
The distinction between principal and interest is especially important. Interest is the cost of borrowing; principal repayment reduces your debt and helps build equity in the property. With a typical fixed-rate mortgage, the principal-and-interest payment stays the same, but the amount allocated to each component changes over time.
Why the Principal and Interest Portions Change Every Month
At the beginning of a fully amortizing mortgage, the outstanding balance is at its highest. Since interest is calculated on the amount still owed, a larger share of the early payments goes toward interest. As the balance falls, the interest charged each month generally falls too, allowing more of the same scheduled payment to reduce principal.
Consider a $300,000 mortgage with a fixed annual interest rate of 6.5% and a 30-year repayment period. Assuming monthly payments and a standard monthly interest calculation, the estimated principal-and-interest payment is about $1,896.20.
| Payment detail |
First month |
Around year 15 |
| Scheduled monthly payment |
$1,896.20 |
$1,896.20 |
| Interest portion |
$1,625.00 |
$1,182.95 |
| Principal portion |
$271.20 |
$713.25 |
| Approximate balance after payment |
$299,728.80 |
$217,677.42 |
The figures are rounded, and the year-15 column represents the 180th payment. Notice that the scheduled payment has not changed, yet the principal portion has grown substantially. This is the central idea behind mortgage amortization: each payment reduces the balance, and the shrinking balance changes how subsequent payments are divided.
How Much of Your Mortgage Will You Still Owe After 5, 10 or 15 Years?
The original loan amount and monthly payment don’t tell you how much principal you will have repaid by a particular date. The remaining balance in an amortization schedule answers that question.
Using the same $300,000 mortgage at 6.5% over 30 years, the approximate balances after selected payments are:
| Milestone |
Remaining principal |
Principal repaid |
| After 5 years |
$280,832.93 |
$19,167.07 |
| After 10 years |
$254,328.38 |
$45,671.62 |
| After 15 years |
$217,677.42 |
$82,322.58 |
| After 25 years |
$96,912.49 |
$203,087.51 |
These estimates assume the interest rate stays at 6.5%, payments are made monthly and on schedule, and there are no extra principal payments or loan changes.
The figures illustrate why looking only at the monthly payment can be misleading. After five years of payments, the borrower has made approximately $113,772 in scheduled principal-and-interest payments, but only about $19,167 has reduced the original principal. The rest has gone toward interest.
This information can be useful if you expect to sell your home, refinance your mortgage, or compare the cost of keeping your current loan with taking out a new one. Your actual sale proceeds will also depend on the property’s market value, selling expenses and any other amounts owed against it.
How Much Interest Will You Pay Over the Full Mortgage?
A manageable monthly payment can still add up to a substantial borrowing cost over several decades. An amortization schedule helps you see that cost in total rather than judging the mortgage by one monthly figure.
For the $300,000 example at 6.5% over 30 years:
| Cost measure |
Approximate amount |
| Original mortgage principal |
$300,000.00 |
| Monthly principal-and-interest payment |
$1,896.20 |
| Total scheduled payments over 30 years |
$682,633.47 |
| Total interest over the repayment period |
$382,633.47 |
The total is based on the unrounded monthly payment, so multiplying the displayed rounded payment by 360 may produce a small difference.
In this example, the total interest over the life of the loan is greater than the original amount borrowed. That doesn’t mean the loan is necessarily unsuitable; it shows why the interest rate and repayment period deserve as much attention as the monthly payment.
These figures cover principal and interest only. Property taxes, homeowners insurance, mortgage insurance, closing costs and other fees may increase the overall cost of owning the home, but they are not automatically part of a standard principal-and-interest amortization calculation.
What Happens When You Choose a 15-Year Instead of a 30-Year Mortgage?
A shorter repayment period generally means a higher required monthly payment but less time for interest to accumulate. A longer period spreads repayment over more months, making the scheduled payment lower while usually increasing the total interest paid.
Here is how the same $300,000 mortgage compares at a fixed 6.5% rate:
| Measure |
15-year mortgage |
30-year mortgage |
| Monthly principal and interest |
$2,613.32 |
$1,896.20 |
| Number of monthly payments |
180 |
360 |
| Total scheduled payments |
$470,397.98 |
$682,633.47 |
| Total interest |
$170,397.98 |
$382,633.47 |
The 15-year option costs about $717 more per month but reduces the estimated lifetime interest by approximately $212,235. The comparison assumes the same starting principal and interest rate, with no additional fees or prepayments.
The right choice depends on your budget and other financial priorities. A shorter mortgage can reduce interest costs, but the higher payment leaves less room for emergencies, retirement contributions or other expenses. Use the calculator to compare repayment periods alongside the monthly payment you can comfortably sustain.
How Extra Principal Payments Can Shorten Your Mortgage
An extra payment directed toward principal can reduce the balance faster than the original schedule anticipates. Because later interest charges are calculated on the remaining balance, reducing principal sooner can also reduce the interest charged in subsequent months.
Suppose you take out a $300,000 mortgage at 6.5% over 30 years and add $100 to the scheduled principal-and-interest payment every month. Under a standard monthly amortization calculation, the extra amount could pay off the mortgage in approximately 26 years rather than 30 and reduce total interest by about $61,000.
The exact result depends on the loan terms, payment timing, rounding and how your lender applies extra payments. This is an illustrative calculation, not a payoff quote from your lender.
Before making additional payments, check whether your mortgage has prepayment limits or penalties. Make sure extra funds are applied to principal rather than being treated as an advance payment of a future instalment. If your lender offers different prepayment options, compare their costs and conditions before committing.
Use the Extra Principal Payment per Month field in this calculator to compare the standard schedule with an accelerated repayment scenario. Review both the revised payoff timeline and the interest estimate; a lower balance today can affect the cost of borrowing for years to come.
When a Standard Mortgage Amortization Schedule May Not Match Your Loan
The usual schedule assumes a defined principal, a known interest rate, regular payments and a repayment structure designed to bring the balance to zero by the end of the amortization period. Some mortgages work differently.
- Adjustable-rate mortgages: If the interest rate changes, the required payment or repayment schedule may need to be recalculated. A schedule based on today’s rate is only a projection if the rate can change.
- Interest-only mortgages: During the interest-only period, payments may cover the interest without reducing the original principal. The balance may remain unchanged until principal repayment begins.
- Balloon mortgages: Payments may be calculated over a longer amortization period than the actual loan term, leaving a large balance due at the end.
- Negative amortization: If a payment does not cover all the interest charged, unpaid interest may be added to the balance, causing the amount owed to increase rather than decrease.
These structures have different repayment implications. If your mortgage includes an interest-only period, a changing rate, a balloon payment or other special terms, check the loan agreement and lender’s schedule instead of assuming a standard fixed-rate projection will represent the full loan.
Mortgage Amortization vs. Mortgage Term: What Is the Difference?
The amortization period is the time over which the mortgage is scheduled to be repaid in full. The loan term is the period during which the current loan contract or interest-rate arrangement applies. Depending on the country and mortgage product, the term may end before the full amortization period has elapsed.
For example, a mortgage may be structured to repay the principal over 25 years while the borrower has a fixed interest rate for only five years. At the end of that five-year term, the borrower may need to renew or refinance the mortgage, depending on the loan agreement and local lending rules. The remaining principal is not automatically paid off simply because the initial term has ended.
Understanding this distinction helps you avoid treating a rate period as the date the whole mortgage will be repaid. If you are comparing mortgages, look at both the scheduled payment and what happens when the current contract or rate period ends.
What This Mortgage Amortization Calculator Includes
This calculator is designed to estimate a mortgage repayment schedule using the principal amount, annual mortgage rate, loan term and optional additional monthly principal payment.
Use it to explore:
- Estimated monthly principal-and-interest payments.
- The projected total interest over the repayment period.
- The total scheduled principal-and-interest cost.
- The expected payoff date.
- How extra monthly principal payments can change the payoff timeline and interest estimate.
The calculation is an estimate based on the inputs and assumptions used by the tool. It may not match a lender’s official schedule exactly because of differences in interest accrual, payment dates, rounding, fees, rate adjustments or how additional payments are processed. It does not replace your mortgage contract or a lender-provided payoff statement.
