Amortization Schedule Calculator

What is an amortization schedule?

An amortization schedule is a complete table of every payment on a fixed-rate loan, showing how each payment is split between interest (the cost of borrowing) and principal (the amount that actually reduces your balance). On an amortizing loan — a mortgage, auto loan, or most personal loans — your payment is the same every month, but the makeup of that payment shifts steadily over time. The schedule also tracks the remaining balance after each payment, so you can see the exact month the loan reaches zero.

The word "amortize" comes from the Latin for "to kill off": each payment slowly kills off the debt. Lenders are required to be able to produce this schedule, but you rarely see it up front — which is why building your own is so useful before you sign. Plug your numbers into the amortization calculator above to generate the full table instantly.

How this amortization calculator works

• Monthly payment. The fixed payment uses the standard amortizing formula M = P · r / (1 − (1 + r)^−n), where P is the loan amount, r is the monthly rate (annual rate ÷ 12), and n is the number of monthly payments (years × 12 + months).
• Each payment. Interest for the month = current balance × monthly rate. Whatever is left of the payment reduces principal: principal = payment − interest. The balance drops by that principal, and the next month's interest is calculated on the new, lower balance.
• Extra payments. Any extra amount is added entirely to principal, so it permanently lowers the balance that all future interest is charged on — which is why even small extra payments compound into large savings.
• Biweekly. When enabled, you pay half the monthly amount every two weeks. That's 26 half-payments a year — equal to 13 full monthly payments instead of 12 — with the 13th going straight to principal.
• Zero interest. If the rate is 0%, the payment is simply the loan amount divided by the number of months.

This matches the result of a spreadsheet built with Excel's PMT() and IPMT()/PPMT() functions. Nothing is sent to a server — all the math runs in your browser, and the "copy link" button just encodes your inputs into the web address.

Why early payments are mostly interest

This is the single most surprising part of amortization. Because interest is always charged on the current balance, and the balance is highest at the start, your earliest payments are dominated by interest. On a $300,000 mortgage at 6.5% over 30 years, the monthly payment is about $1,896 — but in month one, roughly $1,625 of that is interest and only about $271 actually pays down the loan.

Over time the balance falls, so the interest portion shrinks and the principal portion grows, accelerating toward the end. This "front-loading" is exactly why extra payments early in a loan are worth far more than the same payments made years later: an early dollar of principal avoids interest on every single remaining month. It's the mirror image of the compounding that builds wealth in the compound interest calculator — here it's working against you, so cutting the balance early pays off the most.

How extra and biweekly payments save money

Because every extra dollar goes to principal, prepayment is one of the highest-certainty "returns" in personal finance: you save the loan's interest rate, guaranteed, with no market risk. On a 30-year, $300,000 loan at 6.5%, adding just $200 a month typically pays the loan off around 6 years early and saves well over $80,000 in interest. Use the "What paying extra really does" table above to see your exact numbers.

The biweekly strategy works without a big budget change. Paying half your monthly amount every two weeks produces 26 half-payments — 13 full payments a year. That one extra payment, applied to principal, usually trims four to six years off a 30-year mortgage. Before committing, confirm your lender applies biweekly payments to principal immediately and doesn't just hold them, and check there is no prepayment penalty.

Mortgage vs auto vs personal loan amortization

The math is identical for any fully amortizing fixed-rate loan; only the typical terms differ:

• Mortgages are the longest (15 or 30 years), so the front-loaded interest effect is most extreme and extra payments have the biggest impact. Rates are usually the lowest because the home is collateral.
• Auto loans run shorter (typically 3–7 years). Because the term is short, principal builds quickly and total interest is modest compared with a mortgage — but rates can be higher, especially on used cars.
• Personal loans are usually 2–7 years and unsecured, so rates are the highest of the three. Their amortization schedules pay down principal fast, but the high rate makes extra payments especially worthwhile.

Whatever the loan, the schedule answers the two questions that matter: how much will this cost in total, and how much faster can I be free of it? Once you know your target payoff, see how the freed-up cash could grow by feeding it into the retirement calculator.

Frequently asked questions about loan amortization