Amortization Calculator
See a year-by-year loan amortization schedule and how extra payments cut your interest.
An amortization schedule calculator shows how a fixed-rate loan balance changes over time as each payment is split between interest and principal. This calculator uses the loan amount, annual interest rate, term in years, and any extra monthly payment to produce a scheduled payment, total interest, payoff time, and a year-by-year table. That table turns an abstract loan quote into something easier to inspect because you can see how the balance falls at different stages of repayment.
People commonly use a loan amortization calculator when comparing mortgages, refinancing, or deciding whether extra payments are worth the tradeoff. Early in a long loan, a large share of each scheduled payment goes to interest because the balance is still high. Later, more of the payment goes to principal, which helps borrowers compare terms more realistically and judge whether faster payoff fits their cash flow.
How to use the Amortization Calculator
- Enter "Loan amount" as the amount financed, not the purchase price of the home or asset. The calculator treats this figure as the starting principal balance.
- Type the annual "Interest rate" and choose the "Loan term" in years. The tool converts the term into monthly payments and calculates the fixed principal-and-interest payment from those inputs.
- If you plan to pay extra toward principal every month, fill in "Extra monthly payment". Leave it at zero if you want the standard schedule only.
- Read the main "Monthly payment (P&I)" first, then review "Total interest", "Total paid", and "Payoff time". Those lines explain borrowing cost, not just the required monthly amount.
- Use the table to see how the schedule changes by year. The "Principal" and "Interest" columns show where the money goes, while "Balance" shows how much debt remains after each year.
- If you are comparing scenarios, change one variable at a time so the result is easier to interpret.
Formula
Balance(k) = Balance(k−1)·(1+r) − Payment
Example: a mortgage amortization calculator with extra payments
Suppose "Loan amount" is $300,000, "Interest rate" is 6.25%, "Loan term" is 30 years, and "Extra monthly payment" is $200. With those inputs, the calculator shows "Monthly payment (P&I)" of $1,847.15. It also reports "Total interest" of $267,775.51, "Total paid" of $567,775.51, and "Payoff time" of 23 yrs 2 mo.
The scheduled payment of $1,847.15 comes from the standard fixed-rate amortizing loan formula using 360 monthly payments. The extra $200 is not added to that displayed scheduled payment line, but it is applied inside the payoff simulation to reduce principal faster each month. Because of that extra amount, the loan finishes in 23 years and 2 months instead of the full 30 years. The calculator reports "Interest saved" of $97,199.07 and "Months saved" of 82. In the year-by-year table, the first year shows $5,985.34 paid toward principal and $18,580.47 paid in interest, illustrating how interest-heavy early mortgage payments usually are.
How to interpret the result
The main payment line is useful for budgeting, but the amortization schedule calculator becomes more valuable when you look at payoff time and cumulative interest together. Two loans can have similar payments while leading to different costs.
A mortgage amortization calculator with extra payments is especially helpful when your goal is flexibility. Even modest extra principal can shorten the loan because it lowers the balance that future interest is charged on.
If the early rows look discouraging because interest is high, that is normal for fixed-rate amortizing loans. The balance usually declines slowly at first and then accelerates later as more of each payment starts going to principal.
Next, you may also find these useful: Mortgage Calculator, Loan Calculator, Auto Loan Calculator.
Assumptions and limitations
- This calculator assumes a fixed interest rate and equal scheduled monthly principal-and-interest payments for the entire term. It does not model adjustable-rate loans, recasts, or refinancing later.
- Extra payments are treated as regular extra principal paid every month. The tool does not model occasional lump-sum prepayments or lender-specific rules for when extra funds are applied.
- The results focus on loan amortization only. Property taxes, homeowners insurance, mortgage insurance, HOA dues, and maintenance costs are outside the calculation.
- The year-by-year schedule is based on the calculator's internal payment simulation and rounded display values. Formal lender disclosures may differ slightly because of timing conventions or payment processing rules.
Frequently asked questions
What does an amortization schedule calculator actually show?
It shows how repayment changes the loan over time. Instead of only giving a monthly payment, it breaks the schedule into principal, interest, remaining balance, and payoff timing so you can see how the debt changes.
Why does interest take such a large share of the first payments?
Interest is calculated from the remaining balance, and the balance is largest at the beginning. That means early payments tend to be interest-heavy. As the balance falls, interest shrinks and principal grows.
How does a loan amortization calculator help when comparing offers?
It lets you compare more than the headline monthly payment. By reviewing total interest, payoff timing, and the way the balance falls, you can see whether a lower payment is cheaper or simply stretched over more years.
Will a mortgage amortization calculator with extra payments always save money?
If the extra payment is applied directly to principal and there is no prepayment penalty, it generally reduces total interest and shortens the payoff period. The exact benefit depends on balance, rate, and timing.
Is the monthly payment on this page my full housing payment?
No. This calculator's main result is principal and interest only. A homeowner may also owe property taxes, insurance, HOA dues, and maintenance, so the full housing budget can be higher than the loan payment shown here.
When is an amortization schedule less informative?
It is less complete when the loan does not stay fixed. Adjustable-rate mortgages, interest-only periods, refinancing, and irregular prepayments can change the real path. In those cases, the schedule is still useful.
Sources and further reading
- Consumer Financial Protection Bureau: What is amortization?
- Consumer Financial Protection Bureau: Owning a home
- Internal Revenue Service: Publication 936
Last reviewed: 2026-10-02. See our editorial policy.
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Estimates only; not financial, tax or legal advice. Confirm figures with your lender or a licensed professional. Full disclaimer