Mortgage Amortization Calculator — Free Payment Schedule Generator

How to Use the Mortgage Amortization Calculator

This calculator generates a detailed amortization schedule showing exactly how your mortgage payments are applied over the life of the loan. It also analyzes the powerful impact of making extra payments on your total interest costs and payoff timeline.

1. Enter your loan amount. Input the total mortgage principal, which is the home purchase price minus your down payment. For example, if you bought a $350,000 home with 20% down ($70,000), your loan amount is $280,000.
2. Set your interest rate. Enter the annual interest rate from your mortgage agreement or lender quote. The calculator supports rates from 0% to 20%. As of early 2026, the average 30-year fixed rate is around 6.5%.
3. Choose the loan term. Select from 10, 15, 20, 25, or 30-year terms. The term dramatically affects both your monthly payment and total interest paid. Shorter terms mean higher payments but substantially less interest over the life of the loan.
4. Add extra payments (optional). Enter any additional payments you plan to make. You can set extra monthly payments (added to every payment), extra yearly payments (applied once per year), or a one-time lump sum. The calculator shows the full impact of these extra payments on your interest savings and payoff timeline.
5. Review your results. Examine the payment summary at the top, the comparison chart showing balance reduction with and without extra payments, and the complete month-by-month amortization table below. If you entered extra payments, the green summary box shows exactly how much time and money you save.

Adjust any input value to instantly recalculate your entire amortization schedule. This makes it easy to experiment with different scenarios, like comparing the impact of $100 versus $200 in extra monthly payments.

Understanding the Amortization Formula

Mortgage amortization follows a precise mathematical formula that determines how each payment is allocated between principal reduction and interest charges. Understanding this formula helps you see why extra payments are so powerful and why early payments are heavily weighted toward interest.

Where each variable represents:

• M = Monthly payment (principal and interest only)
• P = Loan principal (original loan amount)
• r = Monthly interest rate (annual rate ÷ 12 ÷ 100)
• n = Total number of monthly payments (years × 12)

For each month in the schedule, the interest and principal portions are calculated as:

• Interest portion = Remaining balance × monthly rate
• Principal portion = Monthly payment − interest portion
• New balance = Previous balance − principal portion

Worked Example with Extra Payments

Consider a $280,000 mortgage at 6.5% for 30 years with an extra $200 monthly payment:

1. Calculate base monthly payment: r = 0.065/12 = 0.005417, n = 360. M = $280,000 × [0.005417 × (1.005417)³⁶⁰] / [(1.005417)³⁶⁰ − 1] = $1,770
2. Month 1 without extra: Interest = $280,000 × 0.005417 = $1,517. Principal = $1,770 − $1,517 = $253. New balance = $279,747
3. Month 1 with $200 extra: Interest = $1,517 (same). Principal = $253 + $200 = $453. New balance = $279,547 (saves $200 of principal immediately)
4. Impact over full term: Without extra payments: 360 months, $357,224 total interest. With $200/month extra: approximately 284 months (76 months saved), $279,000 total interest ($78,000 saved)

The savings compound because each month your balance is lower than it would have been, so less interest accrues, meaning even more of your regular payment goes to principal. This snowball effect is why extra payments made early in the loan term generate the largest interest savings.

Practical Amortization Examples

These real-world scenarios demonstrate how amortization works across different loan amounts, terms, and extra payment strategies. Each example uses realistic 2026 market conditions.

New Homeowner: Standard 30-Year Mortgage

Marcus and Elena close on a $320,000 home with a 20% down payment ($64,000), taking a $256,000 mortgage at 6.5% for 30 years. Their monthly payment is $1,618. In their first year, they pay $19,416 total, but only $2,799 goes to principal while $16,617 goes to interest. By year 10, the annual split shifts to $5,285 principal and $14,131 interest. By year 20, they pay $9,999 principal and $9,417 interest. Over the full 30 years, they pay $326,499 in total interest, more than the original loan amount itself.

Aggressive Payoff: Biweekly Payment Strategy

Keisha takes a $240,000 mortgage at 6.25% for 30 years with a monthly payment of $1,478. Instead of paying monthly, she decides to pay half the payment ($739) every two weeks, which amounts to 26 half-payments or 13 full payments per year instead of 12. This extra annual payment of $1,478 is equivalent to about $123/month in extra payments. This simple change reduces her payoff time from 30 years to approximately 24.5 years and saves her about $57,000 in total interest. The biweekly approach works well for people paid every two weeks because it aligns with their income schedule.

Windfall Application: Annual Bonus Toward Mortgage

David has a $300,000 mortgage at 6.75% for 30 years (monthly payment: $1,946). He receives an annual bonus of $5,000 after taxes and decides to apply it to his mortgage as an extra yearly payment. Without the bonus payments, he would pay $400,472 in total interest over 30 years. With the $5,000 annual extra payment, he pays off the mortgage in approximately 22 years and 4 months, saving about $131,000 in interest and 7 years and 8 months on his loan term. The key is consistency: applying the bonus every year maximizes the compounding benefit.

Refinance Analysis: 30-Year to 15-Year

The Wong family has been paying their $280,000 mortgage at 7.0% for 5 years. Their remaining balance is approximately $266,000 with 25 years left, and their monthly payment is $1,863. They refinance to a new 15-year mortgage at 5.75%, with a new payment of $2,206. While their monthly payment increases by $343, their total remaining interest drops from $292,000 (original) to $131,000 (refinanced), saving them $161,000 and finishing 10 years sooner. They use this amortization calculator to confirm the savings before committing to the refinance.

Complete Guide to Mortgage Amortization

Understanding how amortization works empowers you to make smarter decisions about your mortgage, from choosing the right term length to implementing effective extra payment strategies that can save you tens of thousands of dollars.

Why Front-Loaded Interest Matters

Mortgage amortization is front-loaded with interest, meaning you pay disproportionately more interest in the early years. On a typical 30-year mortgage at 6.5%, approximately 86% of your first year payments go to interest. This ratio gradually shifts until, in the final years, nearly all of each payment goes to principal. This structure is not designed to disadvantage borrowers; it is the mathematical consequence of calculating interest on the remaining balance each month. Understanding this helps you appreciate why strategies that reduce your balance early (extra payments, refinancing to shorter terms) have such dramatic impacts on total interest.

Choosing the Right Extra Payment Strategy

There are several ways to accelerate your mortgage payoff. Extra monthly payments are the simplest to set up as a recurring addition to your regular payment. Extra yearly payments work well if you receive annual bonuses or tax refunds. One-time lump sum payments from an inheritance, home equity loan, or savings are immediately impactful. The rounding-up method (rounding your payment from $1,770 to $2,000) is easy to budget for and surprisingly effective. Research shows that consistency matters more than the specific strategy, so choose whichever method you are most likely to maintain over time.

When Extra Payments Make Sense (and When They Do Not)

Extra mortgage payments are most beneficial when your mortgage rate exceeds what you could earn on low-risk investments, when you have already funded retirement accounts and emergency savings, when you value the psychological benefit of debt reduction, and when you plan to stay in the home long enough to realize the savings. Extra payments may not be the best choice if you carry higher-interest debt (credit cards, personal loans), lack adequate emergency savings (3 to 6 months of expenses), could earn a higher after-tax return by investing the money, or plan to sell the home within a few years.

Reading and Using Your Amortization Schedule

Your amortization schedule is a powerful financial planning tool. Each row shows the month number, total payment amount, principal portion, interest portion, and remaining balance. Use it to determine exactly when you will reach 20% equity to eliminate PMI, plan extra payment timing for maximum impact, verify that your lender is correctly applying your payments, compare refinancing scenarios by looking at remaining interest, and set milestone goals (paying off $50,000 in principal by a target date). Saving or printing your schedule provides a roadmap for your entire mortgage journey.

Common Mistakes to Avoid

• Not specifying extra payments as principal-only. When making extra payments to your lender, always clearly designate them as "additional principal" payments. Otherwise, your lender may apply them to the next month payment or hold them in escrow, which reduces or eliminates the interest-saving benefit.
• Ignoring prepayment penalties. Some mortgages, particularly those from before 2014, include prepayment penalty clauses that charge a fee for paying off the loan early or making large extra payments. Check your loan agreement before committing to an aggressive payoff strategy.
• Depleting emergency savings for extra payments. While reducing mortgage interest is valuable, having adequate liquid savings for emergencies is more important. Aim to maintain at least 3 to 6 months of living expenses in savings before directing extra funds to your mortgage.
• Forgetting to recalculate after refinancing. If you refinance, your amortization schedule completely resets. Generate a new schedule to understand your updated principal vs interest split and adjust your extra payment strategy accordingly.
• Comparing only monthly payments between loan terms. A 30-year loan has a lower monthly payment than a 15-year, but the total interest cost is dramatically higher. Always compare total interest paid over the full term, not just the monthly payment amount.