Amortization Table Example: Monthly Loan Breakdown

An amortization table shows how each loan payment is divided between interest and principal, and how the balance changes over time. Enter a loan amount, annual APR, and term below to calculate the monthly payment and total interest; the example table later shows how those payments are allocated.

Formula

The calculator uses a fixed-payment loan formula. It first finds the monthly payment from the principal, monthly interest rate, and number of monthly payments:

Payment = P × r ÷ [1 − (1 + r)⁻ⁿ]

• P is the original loan principal, in dollars.
• r is the monthly interest rate as a decimal: annual APR ÷ 1,200. For an 8% APR, r = 0.08 ÷ 12.
• n is the number of monthly payments: loan term in years × 12.

The calculator rounds the monthly payment to cents. It then calculates total interest as (rounded monthly payment × n) − P. This convention uses the displayed, cent-rounded payment for the total. A real lender may handle a small final-payment adjustment differently.

Worked Example

Using the calculator’s default inputs—$20,000 principal, 8% APR, and a five-year term—the monthly rate is 0.08 ÷ 12 = 0.0066667, and the term is 5 × 12 = 60 payments.

1. Substitute into the fixed-payment formula: $20,000 × 0.0066667 ÷ [1 − (1.0066667)⁻⁶⁰].
2. The unrounded result is approximately $405.53 per month; rounded to cents, the payment is $405.53.
3. Total scheduled payments using that rounded amount are $405.53 × 60 = $24,331.80.
4. Subtract the $20,000 principal: estimated total interest is $4,331.80.

These two outputs summarize the schedule, but they do not show the changing split within each payment. The sample rows below illustrate that split using the same inputs.

Example Amortization Table

For each period, interest is calculated on the balance at the start of the month. Principal repaid is the payment minus that month’s interest, and the ending balance is the starting balance minus principal repaid. Values are shown to cents, so displayed rows can differ slightly from calculations made with unrounded intermediate values.

Payment	Starting balance	Payment	Interest	Principal	Ending balance
1	$20,000.00	$405.53	$133.33	$272.20	$19,727.80
2	$19,727.80	$405.53	$131.52	$274.01	$19,453.79
3	$19,453.79	$405.53	$129.69	$275.84	$19,177.95
60	About $402.85	About $405.53	About $2.69	About $402.84	About $0.01*

*The final row is approximate and reflects cent rounding in the illustrative schedule. A servicer may adjust the final payment to clear the remaining balance. Across the schedule, the interest portion generally falls as the balance declines, while the principal portion rises. This pattern is called amortization.

How to Read and Use the Table

An amortization table is useful for seeing the timeline behind a level monthly payment. It can show how quickly principal is reduced, the interest attributed to each period, and the remaining balance at a particular payment number. For a balance after a payment, look at that row’s ending-balance column; for the balance before it, use the starting-balance column.

The table does not mean that the monthly payment itself is split evenly. In the example, the first month’s interest is $133.33, so about $272.20 of the $405.53 payment reduces principal. Later, the interest charge is calculated on a smaller balance, leaving more of the same payment to reduce principal. The payment remains level under the formula’s assumptions.

In general, a schedule is generated one payment at a time:

• Interest for the period = starting balance × monthly rate.
• Principal paid = payment − period interest.
• Ending balance = starting balance − principal paid.

Use a lender’s actual payment schedule or disclosure when exact dates, fees, payment allocation, or final-payment amounts matter. The calculator is an arithmetic illustration, not an account statement.

Common Errors and Limits

A common mistake is treating an annual APR as the monthly rate. For a monthly-payment calculation, the formula converts an annual percentage to a monthly decimal by dividing by 1,200—not merely by 12. Another mistake is assuming the entire payment reduces principal; interest is paid first in each period under this simplified schedule.

• Variable rates: This calculator assumes the APR stays fixed. If it changes, future payments or the schedule can change.
• Fees and add-ons: The calculation does not include origination charges, taxes, insurance, escrow, or other amounts unless they are included in the entered principal.
• Payment timing: It assumes regular monthly payments and a standard monthly-rate calculation. Actual due dates and day-count conventions can affect lender calculations.
• Rounding: Rounding each row to cents can create small differences from a schedule calculated with greater precision. The lender may adjust the last payment.
• Extra payments: Additional principal payments are not included. They can change the balance path and total interest, depending on how they are applied.

The formula is for a fully amortizing loan with equal scheduled payments. It does not model interest-only periods, balloon payments, skipped payments, or changing payment amounts.

Assumptions

• The interest rate is fixed for the full term.
• Payments are made monthly at regular intervals; the first payment follows the standard monthly schedule.
• Interest is calculated monthly using APR divided by 12, with APR entered as a percentage.
• Fees, taxes, insurance, PMI, escrow, and other charges are not included unless financed in the entered loan amount.

Frequently Asked Questions

What does an amortization table show?
It lists each scheduled payment and separates it into interest and principal, while showing the remaining loan balance after each payment.

Why does the interest portion decrease over time?
With a fixed rate, periodic interest is calculated on the outstanding balance. As principal is repaid and the balance declines, the interest charge generally declines too.

Does an amortization schedule include extra payments?
Not in this calculator. An extra payment can reduce principal sooner, but its effect depends on when it is made and how the servicer applies it. A schedule with extra payments needs those amounts and timing as inputs.

Why might my lender’s table differ by a few cents?
Schedules can differ because of rounding precision, payment dates, day-count methods, fees, or an adjusted final payment. Compare the lender’s disclosed terms and payment schedule for account-specific figures.

Is total interest the same as the total paid?
No. Total scheduled payments include principal and interest. In this example, total payments are $24,331.80, of which $20,000 repays principal and $4,331.80 is estimated interest.

This result is an estimate, and the lender’s disclosure gives the exact figures.

Related

• Roth IRA Earned Income: What Qualifies?
• Qualifying Household Income Calculator
• Qualifying Dependent Gross Income Limit: IRS Rules

in p | Loan amount | $ | 20000 | 1 | 100000000
in apr | Interest rate (APR) | % | 8 | 0.01 | 100
in yrs | Loan term | years | 5 | 0.0833 | 50
out pmt | Monthly payment | $ | p * (apr / 1200) / (1 - (1 + apr / 1200) ^ -(yrs * 12)) | 2
out int | Total interest | $ | pmt * yrs * 12 - p | 2