Amortization Calculator.

Guide

How to use the Amortization Calculator

An amortization schedule is the month-by-month ledger of a loan: what you pay, how much of it is interest, how much reduces the balance, and what you still owe afterward. This calculator builds that schedule for any fixed-rate loan and shows what extra payments do to it.

1. Enter the Loan amount. For a loan you already have, use the current balance and the remaining term rather than the originals.
2. Enter the Interest rate, the annual rate from your loan paperwork.
3. Set the term with Term (years) and + months. A 30-year mortgage is 30 years and 0 months; a 66-month car loan is 5 years and 6 months.
4. Set the First payment date so each row carries a real calendar date.
5. Optionally add an amount in Extra every month, Extra once a year (with the Month of the yearly extra), or One-time extra payment (with the Payment number for the one-time extra). You can combine all three.
6. Switch the Amortization schedule between Yearly and Monthly. Yearly is easier to scan; monthly shows every row.
7. Read the headline Monthly payment, then the Total interest, Total of payments, Payments made and Payoff date, and, if you added extras, the note showing the interest and months saved.

How the math works

Every month the lender charges interest on whatever you still owe: balance times the monthly rate. Your payment covers that interest first, and whatever is left reduces the balance. Next month the balance is a little smaller, so the interest is a little smaller, so a little more of the same payment goes to principal. That slow shift is amortization.

The payment is sized by a formula so that the balance hits zero exactly on the last scheduled month. Because the balance is largest at the start, the early payments are mostly interest.

Extra payments go entirely to principal. They don't change the required payment, but they shrink the balance that next month's interest is charged on, and that effect carries through every remaining month. The loan ends early and the total interest falls.

Worked example

Take a $300,000 loan at 6.5% over 30 years, first payment January 2027. The payment is $1,896.20. Over 360 payments you pay $382,633.47 in interest, so the total of payments is $682,633.47, and the loan is paid off in December 2056.

The first payment splits like this: interest is 300,000 × 0.065 ÷ 12 = $1,625.00, which leaves $271.20 of principal. Only 14.3% of that first check reduces what you owe. Here's how the split shifts over the years:

Payment	Date	Interest	Principal	Balance after
1	Jan 2027	$1,625.00	$271.20	$299,728.80
12	Dec 2027	$1,608.40	$287.81	$296,646.82
120	Dec 2036	$1,380.41	$515.80	$254,328.38
233	May 2046	$946.50	$949.70	$173,789.36
240	Dec 2046	$909.90	$986.30	$166,995.85
360	Dec 2056	$10.22	$1,885.99	$0.00

In the first year you pay $22,754.45 and the balance drops by $3,353.18; the other $19,401.27 is interest. After ten years you've paid off 15.2% of the loan. Principal doesn't overtake interest within a single payment until payment 233, in May 2046, and the balance doesn't fall below half until payment 257. On this loan, 56.1% of everything you pay is interest.

Now put $200 in Extra every month. The loan is paid off in January 2050 after 277 payments, total interest falls to $279,184.67, and you save $103,448.79 and 83 months. You put in about $53,900 of extra money (the final payment is a partial one) and avoid nearly twice that in interest, plus almost seven years of payments.

What the schedule tells you

Where your money went. If you sell or refinance after a few years, the balance column is what you'll owe. Someone who sells after ten years still owes $254,328.38 on this $300,000 loan despite having paid $227,544. That's the shape of a long loan.

When extra payments matter most. Early. A One-time extra payment of $10,000 at payment 1 saves $53,601.51 and 33 months; the same $10,000 at payment 120 saves $24,871.14 and 18 months. Both are good, but the first is more than twice as good, because the money has more months of interest to cancel.

Term versus extras. A 15-year loan on the same $300,000 at 6.5% costs $2,613.32 a month, $717.12 more than the 30-year payment, and total interest is $170,397.98 instead of $382,633.47. Extra payments on a 30-year loan get you partway there while leaving you the option to stop. Even one extra payment a year, spread out as $158.02 a month, cuts 70 months and $87,256.29 of interest.

Common mistakes

• Entering the original loan when you want today's picture. Use the current balance and the months left so the payment matches your statement.
• Assuming extras are automatic. Some servicers treat money above the payment as an early payment of next month's bill, not as principal. Tell them in writing that extras go to principal, then check the next statement.
• Comparing total interest across terms as if the payments were equal. A shorter loan always shows less interest, but it demands a bigger check every month. Compare the payment you can sustain, not just the interest column.
• Treating a daily-interest loan as monthly. Some loans accrue interest daily, so paying early in the cycle saves a little. This schedule uses monthly compounding, which is how mortgages and most fixed installment loans are quoted.

When to use the other calculators

For a home purchase, the Mortgage Calculator adds property tax, insurance, PMI and HOA dues to the same schedule. For a car, the Auto Loan Calculator handles the price, trade-in, tax and fees that set the loan amount. If you know the payment you can afford but not the loan amount, rate or term, the Loan Calculator solves for the missing piece.

What this calculator doesn't do

The schedule is an estimate for a fixed-rate loan with monthly compounding and payments made on time. Your lender's statement governs. Real loans may accrue interest daily, round differently, charge late fees, or carry a prepayment penalty that eats into the savings shown here.

It doesn't model adjustable rates, interest-only periods, balloon payments or escrow for taxes and insurance, and it assumes any extra payment is applied to principal on the date you say it is.

Frequently asked questions

Estimates for planning only. Your lender, dealer or tax authority sets the real numbers, and rates, fees and rules change. This is not financial, tax or legal advice. Nothing you type here leaves your browser. See the terms of use.