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Amortization Calculator

Build a complete month-by-month amortization schedule for any fixed-rate loan. See exactly how every payment splits between interest and principal, watch the balance fall, and find out what the loan really costs. Runs in your browser — nothing is submitted.

$10,000
$500$100,000
6 mo120 mo
1%36%

Works for any fixed-rate loan repaid in equal monthly installments. Fees such as origination are not included.

Every payment

Your amortization schedule

Copper rows mark the end of each year. Scroll to watch the interest column shrink and the principal column grow — that shift is the whole story of a loan.

MonthPaymentInterestPrincipalBalance

Figures are rounded to the nearest cent; the final payment is adjusted so the balance lands exactly on zero.

The math

How amortization works

"Amortizing" just means killing the debt gradually with equal payments. The payment never changes — but what it does changes every single month.

M = P × r ÷ (1 − (1 + r)−n)
M = monthly payment · P = amount borrowed · r = annual rate ÷ 12 · n = number of months

The month-by-month loop

Once the payment is fixed, the schedule builds itself with three steps repeated every month:

  1. Interest = current balance × monthly rate.
  2. Principal = payment − interest.
  3. New balance = old balance − principal. Repeat.

That is it. There is no trick — the entire table above comes from those three lines.

Why the split flips

Interest is charged on what you still owe, so when the balance is biggest the interest bite is biggest. On $10,000 at 15% over 60 months, month one is $125 interest and $112.90 principal. The final month is almost entirely principal.

Because each payment shrinks the balance a little, next month's interest is slightly smaller — so slightly more goes to principal. Repeat sixty times and the curve tips over completely.

Why paying extra early wins

An extra dollar paid in month one removes a dollar of balance for all 59 remaining months, so it dodges interest 59 times. The same dollar paid in month 59 dodges it once. That asymmetry is why front-loading extra payments is worth so much more than back-loading them.

Reading the table

What each column means

Payment

Fixed for the whole term. Identical in month 1 and month 60 — only its job changes.

Interest

The lender's fee for that month, charged on the balance you carried into it. Biggest at the start.

Principal

The part that actually reduces the debt. This is the number you want to grow — extra payments land here.

Balance

What is left after that payment. Falls slowly at first, then accelerates as the interest bite weakens.

An estimate, not an offer. Great Plains Lending is a loan-matching service, not a lender. This schedule assumes a fixed rate and equal monthly payments, and excludes origination fees, late fees and insurance. It does not model variable rates, interest-only periods or balloon payments. Your lender's own schedule governs your loan.
Answers

Amortization calculator FAQ

What is an amortization schedule?

A table listing every payment over the life of a loan. Each row shows the payment, how much goes to interest, how much reduces principal, and the balance left. The payment stays constant, but the split shifts steadily toward principal as the balance falls.

How is amortization calculated?

The fixed payment comes from M = P × r ÷ (1 − (1 + r)−n). Then each month: interest = balance × r, principal = payment − interest, new balance = balance − principal. Repeat until zero.

Why is most of my early payment going to interest?

Interest is charged on what you still owe, and early on you owe the most. On $10,000 at 15%, month one is $125 interest and about $113 principal. As the balance shrinks, the interest portion shrinks with it and more of the same payment hits principal.

Does paying extra change the schedule?

Yes, a lot. Extra money goes straight to principal, so next month's interest is charged on a smaller balance. That compounds — the loan ends earlier and total interest drops. Extra paid early is worth far more than the same amount paid late.

Can I use this for any loan?

Any fixed-rate loan repaid in equal monthly installments — personal loans, installment loans, auto loans, most fixed mortgages. It does not model variable rates, interest-only periods or balloon payments, and excludes fees.

Is the schedule the same as a payoff quote?

No. The schedule shows the balance at each month-end assuming scheduled payments. A lender's payoff quote is the balance plus interest accrued to the exact payoff date and may include fees, so it can differ slightly.

Does using this calculator affect my credit?

No. It runs entirely in your browser, asks for no personal details, and performs no credit check. Nothing is submitted when you move the sliders.

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