An amortization schedule is the month-by-month (or year-by-year) map of how a fixed-rate loan gets paid off. It answers the question every borrower eventually asks: where is my money actually going? Early on, the answer is uncomfortable — most of each payment is interest. This calculator builds the full schedule, shows the principal/interest split for every period, and lets you see exactly how an extra monthly payment rewrites the timeline.
Amortization Schedule Calculator
See exactly how each payment splits between principal and interest, and how the balance falls year by year.
| Year | Principal | Interest | Extra | Balance |
|---|
Estimates only. Assumes a fixed rate and on-time payments. Not a loan offer or financial advice.
How to use this calculator
Enter the loan amount, interest rate and term. The headline stats show your monthly payment, total interest over the life of the loan, and the payoff date. Toggle between a yearly summary and the first 12 months to see the early-loan interest load up close. Add an extra monthly amount to watch the payoff date jump forward and total interest collapse.
Why early payments are mostly interest
Interest each month is charged on the remaining balance. At the start, that balance is the entire loan, so the interest slice is large and the principal slice is small. As principal chips the balance down, next month’s interest is slightly smaller, so slightly more of the fixed payment goes to principal. This compounding-in-reverse is why a 30-year loan builds equity painfully slowly in years 1–7 and then accelerates.
On a $320,000 loan at 6.5% over 30 years, the first payment is roughly $1,733 interest and only $289 principal. It takes about 18 years before the principal portion finally exceeds the interest portion.
The power of one extra payment
Because every extra dollar of principal permanently removes that dollar (and all its future interest) from the schedule, even small extra payments have outsized effects:
- $100/month extra on a $320k / 30-year / 6.5% loan saves roughly $70,000 in interest and cuts about 5 years off the term.
- One full extra payment per year (achieved by paying biweekly) typically removes 4–6 years from a 30-year mortgage.
The earlier the extra payments happen, the larger the effect, because they remove principal when the interest-per-dollar is highest.
Yearly vs monthly view
The monthly view exposes the brutal early split most borrowers never see. The yearly view is better for planning — it shows how much equity you build per year and when the loan crosses key milestones. Both use the exact same math; only the grouping differs.
Frequently asked questions
Is the schedule exact? Yes, for a fixed rate and on-time payments. The standard amortization formula is deterministic. Real loans can vary if the rate is adjustable, payments are late, or escrow amounts change — but the principal-and-interest core is precisely what this shows.
Does extra payment go straight to principal? With most US mortgages, yes — but you must confirm the lender applies extra funds to principal, not to “prepaid interest” or the next payment. Many lenders need you to specify “apply to principal.”
Why does my lender’s number differ slightly? Rounding and day-count conventions. Lenders may use actual/365 or 30/360 interest accrual; this calculator uses the standard monthly method. Differences are typically a few dollars.
Should I pay extra or invest instead? Guaranteed return equal to your mortgage rate (paying down a 6.5% loan is a risk-free 6.5% return) versus uncertain market returns. At today’s rates the math favors extra payments more than it did in the 3% era — but it depends on your full financial picture.
What is negative amortization? When the payment does not even cover the interest, so the balance grows. Standard fixed mortgages never do this; some adjustable or interest-only products can. This calculator models only positive-amortizing loans.
Does a shorter term change the schedule shape? Yes. A 15-year loan front-loads far less interest — principal overtakes interest within the first few years — which is why total interest is dramatically lower despite the higher payment.
Can I see the schedule for a car or student loan? Yes. Any fixed-rate amortizing loan works — enter its balance, rate and term. The math is identical regardless of what the loan is for.
Methodology
Payments use the standard fixed-rate amortization formula. Each period, interest is computed on the opening balance, the remaining payment reduces principal, and any extra amount is applied directly to principal (capped so the loan never overpays). Payoff date counts from the current month assuming on-time payments. Figures are estimates for planning and education — not a loan offer or financial advice.
Written by the CalcCottage team. We show the real number, not the marketing number.
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