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Amortization Calculator

What Is Loan Amortization?

Loan amortization is the process of paying off a debt through regular, scheduled payments over a set period of time. Each payment is divided between two components: interest (the cost of borrowing) and principal (reducing what you owe). In the early years of a loan, the majority of each payment goes toward interest. As you progress through the schedule, more of each payment is applied to principal. This gradual shift is why an amortization schedule is so valuable — it shows exactly where your money goes with each payment and helps you understand the true cost of borrowing. Understanding amortization empowers you to make strategic decisions, such as when to make extra payments or whether refinancing makes financial sense.

How the Amortization Calculator Works

This calculator uses the standard amortization formula to determine your fixed periodic payment based on your loan amount, interest rate, and term. It then generates a complete payment-by-payment schedule showing the interest portion, principal portion, and remaining balance for each payment. The formula divides your annual interest rate by the number of payment periods per year, then uses this periodic rate to calculate a fixed payment that fully amortizes the loan over the specified term. When you enable extra payments, the calculator applies those additional amounts directly to the principal balance, recalculating interest savings and the shortened payoff timeline. The biweekly comparison shows how splitting your monthly payment into 26 bi-weekly payments (equivalent to 13 monthly payments per year) accelerates your payoff.

Frequently Asked Questions

What is an amortization schedule?

An amortization schedule is a detailed table showing every payment over the life of your loan. For each payment, it breaks down how much goes toward interest versus principal, and shows the remaining balance. Early payments are mostly interest, while later payments are mostly principal. This schedule helps you understand the true cost of your loan and plan extra payment strategies.

How do extra payments reduce my total interest?

Extra payments go directly toward reducing your principal balance. Since interest is calculated on the remaining balance, a lower principal means less interest accrues each period. This creates a compounding effect — each extra dollar paid toward principal saves more than a dollar in future interest. Even small extra payments can save thousands over the life of a long-term loan.

What's the difference between biweekly and monthly payments?

With monthly payments, you make 12 payments per year. With biweekly payments, you pay half the monthly amount every two weeks, resulting in 26 half-payments (equivalent to 13 full monthly payments per year). That extra payment each year goes entirely to principal, which can shorten a 30-year mortgage by about 4-5 years and save tens of thousands in interest.

Does this calculator work for different loan types?

Yes! This amortization calculator works for any fixed-rate installment loan including mortgages, auto loans, student loans, personal loans, and business loans. Simply enter your loan amount, interest rate, and term. The presets provide typical values for common loan types to get you started quickly.

Why does so much of my early payment go to interest?

In a standard amortized loan, interest is calculated on the remaining balance. At the start, your balance is at its highest, so the interest charge is large. As you gradually pay down the principal, less interest accrues and more of each payment goes toward principal. For example, on a $300,000 mortgage at 6.5%, your first payment includes about $1,625 in interest but only $271 toward principal.

What is the interest-to-principal ratio?

This is a unique metric that shows how much you pay in interest for every dollar you borrowed. For example, a ratio of $0.63 means you pay 63 cents in interest for every $1 of principal. This helps you quickly assess the true cost of borrowing — higher ratios indicate more expensive loans, typically from higher rates or longer terms.

Should I make extra payments or invest the money instead?

Compare your loan interest rate to potential investment returns. If your loan rate is higher than expected investment returns (after taxes), extra payments make sense. If your loan rate is low (e.g., 3-4%) and you can invest at higher returns (e.g., 7-10% historically in stocks), investing may be more profitable. However, paying off debt also provides a guaranteed, risk-free return and peace of mind.

How accurate is this amortization calculator?

This calculator uses the standard amortization formula used by banks and financial institutions worldwide. Results match official bank calculations for fixed-rate loans. However, actual payments may vary slightly due to rounding, varying month lengths, or additional costs like taxes, insurance, and fees that aren't included in the base amortization calculation.