Amortization Schedule Calculator

What an amortization schedule shows

Every mortgage payment, no matter how the lender markets it, splits into the same two parts: interest to the lender for the month and principal that reduces what you owe. An amortization schedule is just a table of every payment's split, with a running balance.

On a $320,000 loan at 6.5%:

The principal share grows each month because every dollar of principal you pay shrinks the balance, which shrinks next month's interest. The schedule below the calculator tracks every row of that progression for your loan.

The standard amortization formula

The total payment comes from the same annuity formula every amortization tool uses:

M = P × r(1+r)ⁿ ÷ ((1+r)ⁿ − 1)

where P is the principal, r is the monthly rate (annual rate ÷ 12), and n is the number of monthly payments. For a $320,000 loan at 6.5% over 30 years that yields $2,022.

Calculating the monthly payment is simple. To get the principal and interest breakdown for each period, we calculate month by month:

interest = balance × monthly_rate
principal = payment − interest
new_balance = balance − principal

Repeat 360 times and you get the full schedule. The loan amortization and mortgage payment calculators use the same engine; this one just exposes the row-by-row breakdown.

Where the principal share matters

Three decisions turn on the mix, not just the dollar amount:

1. Where your extra principal actually goes. Pay $200 extra in month 1, and that $200 goes almost entirely to principal — which means less interest next month too. Pay $200 extra in month 359 and it is still mostly principal, but the lifetime savings are tiny. Most of the return on extra principal happens early, when the interest share is largest.
2. What a refinance actually changes. Looking only at the monthly payment misses whether a refinance actually saves money. If your refinance extends the term to 30 years again, the early principal share drops sharply — the calculator on this site's refinance page compares lifetime interest to flag that trap.
3. The PMI removal date. PMI cancels when the balance reaches 78% of the original price (or 80% with a request), not at a fixed date. The PMI calculator estimates that month from the running balance.

Read the year-by-year table

The default view in the calculator is a year-by-year summary, not 360 rows:

• Year — calendar year of payments 1-12, 13-24, etc.
• Payment — total of 12 monthly payments.
• Principal — how much of those 12 payments reduced your balance. This column grows every year.
• Interest — how much went to the lender. This column shrinks every year.
• Balance — the running loan balance at the end of the year. On the default example the balance falls below $250K in year 13, $200K in year 19, and $150K in year 23 — the points at which refinancing and PMI removal start to make sense.
• Principal % — annual share going to principal. A 30-year loan at 6.5% starts at 14.7% and crosses 50% in year 20.

How to use this calculator

The page opens with $320,000 at 6.5% for 30 years, so the table fills in immediately:

1. Adjust Loan amount to match what you owe (or expect to borrow). Use the actual loan after any down payment and rolled fees, not the home price.
2. Set Interest rate to your lender's quote. A 0.25% change cascades into four figures of lifetime interest on a 30-year loan.
3. Pick Loan term from the menu (10, 15, 20, or 30 years). The table rebuilds from scratch — switch it to see how much less interest a shorter loan costs.
4. Read the summary cards: Monthly payment (P&I), Total interest paid over term, Total of all payments, and the How the principal/interest mix shifts card comparing year 1 and the final year.
5. Open the Year-by-year schedule table for the full breakdown. Sort by what matters to your decision — interest paid if you're considering refinance; balance crossing 78% if you're planning around PMI.

Amortization FAQ

What does amortization mean?

Amortization is the process of paying off a debt with regular, fixed payments over time. Each payment covers the interest that has accrued since the last payment and the rest reduces principal. Early on, most of the payment is interest; near the end, almost all of it is principal. The full schedule is what an amortization table shows.

What is a 30-year amortization schedule?

It is a 360-row table of every monthly payment on a 30-year fixed-rate loan, showing the principal/interest split and running balance. Most mortgage disclosures include a shorter version. The full year-by-year view above is the comprehensive form.

How does an amortization schedule help with paying off a loan early?

Every extra dollar of principal reduces the balance, which reduces future interest. Paying $100 extra in month 1 saves more than $100 extra in month 300. Run the schedule at year 5 and at year 25 — the difference in remaining interest is what prepayment is buying you, year by year.

How is amortization different from depreciation?

Amortization spreads loan payments across a fixed schedule. Depreciation is an accounting concept that spreads the cost of an asset across its useful life for tax purposes. Mortgage amortization has nothing to do with asset depreciation in the tax sense.

What is negative amortization?

Negative amortization happens when the monthly payment does not cover the interest that has accrued, so the unpaid interest is added to the balance. The balance grows instead of shrinking, even though the borrower is paying. Interest-only loans and some subprime loans can have periods of negative amortization. The standard fixed-rate loan the default here assumes never does.

How do I read the year-by-year totals?

Each row is the sum of 12 monthly payments. Payment is the dollar amount going out, Principal reduces what you owe, Interest is what the lender kept, Balance is what you still owe at year-end, and Principal % is the share of that year's cash flow going to balance reduction — a single number that captures how far through the loan you are.

Why does my last payment differ from the others?

Small rounding accumulates over 360 months. The last payment is adjusted up or down by a few cents to clear the remaining balance exactly. If you trust the lender's schedule over yours, that is why — they are doing the same math at higher precision.

Sources: Amortization math is a standard textbook formula, used identically by lenders, regulators, and consumer disclosure documents (the federal TILA disclosure in particular). All numbers on this page reflect scheduled payments only; prepayment, rate changes, and PMI/MIP adjust the schedule and are not modeled here. Related tools: refinance calculator, mortgage with PMI, and the finance calculators hub.

Disclaimer: This calculator provides informational estimates only and is not financial advice. Your lender's amortization schedule is the authoritative document; differences of a few cents come from rounding precision.