Amortization Schedule Calculator — Full Payment Table

Build the complete payment table for any fixed-rate loan: how much of each payment is interest, how much actually reduces the balance, and what happens when you pay extra every month.

Your payment schedule

How this calculator works

A fixed-rate amortizing loan uses the standard annuity formula: payment = P × r ÷ (1 − (1 + r)⁻ⁿ), where P is the principal borrowed, r is the monthly rate (annual rate ÷ 12) and n is the number of payments. For $300,000 at 6% over 30 years that produces $1,798.65 a month.

Each row of the schedule then repeats the same three steps. Interest for the month is the current balance times the monthly rate. Whatever is left of your payment becomes principal and reduces the balance. Then the balance carries into the next row. Because the payment is fixed and the interest shrinks as the balance shrinks, the principal portion grows every month — slowly at first and quickly later. This is why half of a 30-year mortgage's term can pass with only about a quarter of the principal repaid.

Extra payments simply add to the principal portion of the current row, which shortens the loop. The tool rebuilds the whole table from scratch whenever you change an input, so a negative schedule — where your payment is smaller than the monthly interest — is detected immediately and reported as never paying off rather than generating thousands of useless rows.

Reading your own schedule

Three checkpoints tell you almost everything about a loan's shape. Look at payment 1: the ratio of interest to principal there is the worst it will ever be, so it sets how slowly equity builds at the start. Find the crossover month where principal first exceeds interest — on a 30-year loan it arrives around the second half of the term, which is why refinancing or selling early can feel disappointing. Finally, total up the interest column and compare it against the amount borrowed: paying more in interest than principal is normal for long-term loans, not a warning sign.

The same table also decides whether refinancing is worth it. Compare the remaining rows on your existing loan against a new quote at the lower rate, then divide the closing costs by the monthly saving to get a break-even month count. If you expect to move before that point, the refinance loses money regardless of how attractive the headline rate looks.

Frequently asked questions

What is an amortization schedule?

It is a table of every scheduled payment on a loan, split into interest and principal, with the remaining balance after each one. On a fixed-rate loan the payment stays the same while the split moves: the first payment on a $300,000 30-year loan at 6% sends $1,500 to interest and about $299 to principal, while the last payment is almost entirely principal. Lenders produce one at closing, and this calculator builds the same thing from your own figures so you can test scenarios such as extra payments before committing to them.

How much does an extra $200 a month save?

On a $300,000 30-year loan at 6%, adding $200 a month shortens the loan from 360 payments to roughly 279 and cuts total interest from about $347,515 to about $256,341 — about $91,000 saved, and the loan ends about 6 years 9 months early. The earlier you start, the larger the saving, because extra principal reduces the balance that every future interest charge is calculated on. Starting the same $200 in year ten instead of year one saves materially less.

Why is most of my early payment interest?

Interest each month is the balance multiplied by the monthly rate, so a large balance produces a large interest charge and leaves little of the fixed payment for reducing principal. As the balance falls the interest falls with it and the principal share grows. It is arithmetic rather than a penalty: at no point is the lender taking more than the agreed rate. The practical consequence is that extra payments made early in a loan do far more work than the same payments made late, which is the whole argument for paying ahead in the first few years.

How is the monthly payment calculated?

The standard annuity formula is payment = P × r ÷ (1 − (1 + r)⁻ⁿ), where P is the principal, r is the monthly rate (annual rate divided by 12) and n is the total number of payments. For $300,000 at 6% over 30 years that gives $1,798.65 a month, or $647,514.57 paid in total, of which $347,514.57 is interest. The formula assumes payments are made at the end of each month and that the rate never changes — true for a fixed mortgage or auto loan, not for an adjustable product.

Does this include taxes, insurance and PMI?

No. This is principal and interest only, which is what an amortization schedule covers. A real mortgage payment usually adds property tax, homeowners insurance and possibly private mortgage insurance, collected into an escrow account and changing every year as assessments move. Auto and student loans have no escrow, so principal and interest is typically the whole payment. If you are budgeting for a house, add those escrow items on top of the figure above.

Are there penalties for paying a loan off early?

Most US mortgages, auto loans and federal student loans have no prepayment penalty, so extra principal is allowed freely. Some private student loans, home equity lines and personal installment loans still contain early-payoff clauses, and loans written with precomputed interest collect the full scheduled interest no matter when you finish. Check your agreement for the exact wording, and when you do send extra money, instruct the lender in writing that it should be applied to principal rather than held as an advance payment toward next month.

Last updated Oct 6, 2026 — rates and terms change often, so confirm figures with your lender.

Estimates for general information only, not financial advice — see our disclaimer.

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