Amortization Schedule Calculator
Understand exactly where every dollar of your loan payment goes. Our free amortization calculator generates a complete loan amortization schedule with interactive charts, showing the principal and interest breakdown for each payment. Whether you have a mortgage, auto loan, or personal loan, see how extra payments can save you thousands and help you become debt-free faster.
Principal vs. Interest Over Time
Total Cost Breakdown
5 Key Insights About Loan Amortization
Front-Loaded Interest
In the first year of a 30-year mortgage at 6.5%, roughly 68% of each payment goes straight to interest. This front-loading is why the balance drops so slowly at first—and why early extra payments are so powerful.
The Extra Payment Multiplier
An extra $100/month on a $300,000 mortgage at 6.5% saves over $34,000 in interest and pays off the loan more than 5 years early. Each extra dollar avoids years of compounding interest on that portion.
15 vs. 30-Year Trade-Off
A 15-year mortgage has higher monthly payments but pays dramatically less total interest. On a $300K loan at 6.5%, you'd save over $250,000 in interest—more than the home's original price—by choosing a 15-year term.
Bond Amortization Works Differently
Bond amortization schedules track the gradual adjustment of a bond's book value toward its face value over time. Premium bonds amortize downward; discount bonds amortize upward. Unlike loan amortization, bond schedules use the effective interest method.
Rate Impact Is Non-Linear
Going from 5% to 6% adds roughly $60,000 in total interest on a $300K 30-year mortgage. Going from 6% to 7% adds about $72,000. Higher rates amplify each incremental increase—making rate shopping one of the highest-value financial decisions you can make.
What Is Amortization?
Amortization is the process of spreading a loan into a series of fixed payments over time. Each payment is split between two components: interest (the cost of borrowing) and principal (the actual debt repayment). With each successive payment, the interest portion shrinks and the principal portion grows—a characteristic known as the amortization schedule's "tipping point."
Think of it this way: when you take out a $300,000 mortgage at 6.5% for 30 years, your monthly payment stays fixed at $1,896. But in month one, $1,625 of that payment goes to interest and only $271 goes toward reducing your balance. By month 180 (the halfway point), the split is roughly equal. And by the final years, nearly the entire payment goes to principal.
This applies to mortgage amortization, auto loan amortization, student loans, and any fixed-rate installment loan. Understanding your amortization table empowers you to see the true cost of borrowing and make smarter decisions about extra payments, refinancing, or choosing between loan terms.
The Amortization Formula Explained
The standard formula for calculating monthly amortization payments is:
M = P × [r(1 + r)n] / [(1 + r)n − 1] Where:
- M = Monthly payment amount
- P = Principal loan amount (the total borrowed)
- r = Monthly interest rate (annual rate ÷ 12)
- n = Total number of payments (loan term in years × 12)
Step-by-Step Calculation Example
Let's walk through a $250,000 loan at 6% annual interest for 30 years:
- Convert the annual rate to monthly: r = 6% ÷ 12 = 0.5% = 0.005
- Calculate total payments: n = 30 × 12 = 360 months
- Plug into the formula: M = 250,000 × [0.005 × (1.005)360] / [(1.005)360 − 1]
- Solve (1.005)360: ≈ 6.02258
- Numerator: 250,000 × [0.005 × 6.02258] = 250,000 × 0.030113 = $7,528.25
- Denominator: 6.02258 − 1 = 5.02258
- Monthly payment: M = $7,528.25 ÷ 5.02258 ≈ $1,498.88
Over 360 payments, you'd pay $539,595 in total—meaning $289,595 is pure interest. The amortization graph shows how each payment's principal-interest split evolves across these 360 periods.
How Extra Payments Accelerate Your Payoff
Extra payments are applied directly to the principal, which has a compounding effect. When you reduce the principal, every future payment's interest charge is smaller—so even more of each subsequent payment goes to principal. This virtuous cycle can dramatically shorten your loan term and reduce total interest paid.
For example, adding just $200/month in extra payments to a $300,000 mortgage at 6.5% over 30 years would save you approximately $62,000 in interest and pay off the loan nearly 8 years early. The earlier you start making extra payments, the greater the impact, because you're cutting into the principal during the period when interest charges are highest.
Use the calculator above to experiment with different extra payment amounts and see the exact impact on your amortization schedule, total cost, and payoff timeline.
Frequently Asked Questions
What is an amortization schedule?
An amortization schedule is a detailed table showing every periodic payment on a loan, broken down into principal and interest components. It reveals exactly how much of each payment goes toward reducing your balance versus paying interest, and tracks the remaining loan balance after every payment until the loan is fully paid off.
How does the amortization formula work?
The standard amortization formula is M = P[r(1+r)^n]/[(1+r)^n - 1], where M is the monthly payment, P is the principal loan amount, r is the monthly interest rate (annual rate divided by 12), and n is the total number of payments. This formula calculates a fixed monthly payment that fully repays the loan over the specified term.
How do extra payments affect my amortization schedule?
Extra payments are applied directly to the principal balance, which reduces the outstanding amount that accrues interest. This creates a compounding savings effect: you pay less total interest over the life of the loan and can potentially pay off the loan months or even years early. Even small extra monthly payments can save thousands in interest.
What is the difference between amortization for a mortgage vs. an auto loan?
While both use the same amortization formula, mortgage loans typically have longer terms (15-30 years) and lower interest rates, meaning a larger portion of early payments goes to interest. Auto loans are shorter (3-7 years) with higher rates, so principal reduction happens faster. The amortization table structure is identical for both.
Why do I pay more interest at the beginning of a loan?
Interest is calculated on the outstanding balance each period. At the start of a loan, your balance is at its highest, so the interest charge is largest. As you make payments and the balance decreases, less of each payment goes to interest and more goes to principal. This is called front-loaded interest and is a fundamental characteristic of amortized loans.