Amortization Calculator

An Amortization Calculator builds a complete payment-by-payment schedule for any installment loan, showing exactly how each payment is split between interest and principal over the life of the loan. You enter the loan amount (principal), the annual interest rate, and the term in months or years, and the tool computes the fixed monthly payment along with a row-by-row breakdown of the declining balance. Because amortizing loans front-load interest, the early payments are mostly interest while later payments increasingly chip away at principal.

Under the hood, the calculator uses the standard amortization formula: the fixed payment equals P times r times (1+r)^n divided by ((1+r)^n minus 1), where P is the principal, r is the periodic (monthly) interest rate, and n is the total number of payments. For each period it multiplies the outstanding balance by the periodic rate to get the interest portion, subtracts that from the payment to get the principal portion, and reduces the balance accordingly. This loop repeats until the balance reaches zero on the final payment.

Amortization schedules are useful far beyond home loans. They apply to mortgages, car loans, student loans, personal loans, and business term loans, and they reveal the true total interest cost that a single monthly payment figure hides. Comparing schedules side by side helps you see how a shorter term or a lower rate dramatically reduces lifetime interest, which is why this tool pairs naturally with a Mortgage Calculator, a Car Loan Calculator, or a Refinance Calculator.

A practical tip is to look at the cumulative interest column rather than just the monthly payment, since two loans with identical payments can have very different total costs depending on term length. You can also model extra principal payments to see how much interest you save and how many months you shave off, an approach that complements a Debt Payoff Calculator when prioritizing which balances to attack first.