APR Amortization Table: Monthly Payment and Interest

An APR amortization table shows how each scheduled loan payment is divided between interest and principal, and how the balance changes over time. Enter the loan amount, APR, and term below to calculate the monthly payment and total interest; the results use a fixed-rate, monthly-payment estimate.

Formula

For a fixed-rate loan with equal monthly payments, the payment is calculated from the loan principal, monthly interest rate, and number of payments:

Payment = round[P × r ÷ (1 − (1 + r)⁻ⁿ), 2]

• P is the starting loan principal, in dollars.
• r is the monthly interest rate as a decimal: APR ÷ 1,200. For an 8% APR, r = 8 ÷ 1,200.
• n is the number of monthly payments: loan term in years × 12.
• Payment is the scheduled monthly amount, rounded to the nearest cent.

Total interest in this calculator is (monthly payment × n) − P. It uses the rounded monthly payment, so the displayed total follows the calculator’s cent-rounded payment rather than an unrounded theoretical amount.

Worked Example

Using the default inputs—$20,000 principal, 8% APR, and a five-year term:

1. Convert APR to a monthly decimal rate: 8 ÷ 1,200 = 0.0066667.
2. Find the number of payments: 5 × 12 = 60.
3. Substitute in the payment formula: $20,000 × 0.0066667 ÷ [1 − (1 + 0.0066667)⁻⁶⁰].
4. Round the result to cents: the monthly payment is $405.53.
5. Calculate total interest using that rounded payment: ($405.53 × 60) − $20,000 = $4,331.80.

These are summary figures, not the individual rows of a full schedule. A row-by-row table would apply interest to the balance for each period, subtract the principal portion of the payment, and repeat until the loan is paid off. The last payment can differ slightly when a lender adjusts for rounding or payment dates.

Assumptions

• The APR is fixed for the entire term.
• Payments are equal, made monthly, and applied at the end of each monthly period.
• Interest is modelled monthly at APR ÷ 12.
• Fees, taxes, insurance, PMI, escrow, late charges, and payment-date variations are not included.

How an APR Amortization Table Works

In an amortizing loan, each regular payment covers the interest accrued for the period and pays down some principal. At the start, the balance is larger, so the interest portion is generally larger. As principal is repaid, less interest accrues per period, leaving more of the same scheduled payment to reduce principal.

For a basic monthly schedule, calculate period interest as the opening balance multiplied by the monthly rate. Subtract that interest from the scheduled payment to find principal repaid. Then subtract principal repaid from the opening balance to get the next balance. For example, with the default figures, first-month interest is approximately $133.33 ($20,000 × 0.0066667); the remaining roughly $272.20 of the $405.53 payment reduces principal. Small differences can appear because each figure is rounded to cents.

A table commonly includes the payment number or date, opening balance, payment, interest, principal, and closing balance. The balance column helps answer how much principal remains after a given number of payments. The total-interest figure helps show the interest across the full scheduled term, assuming every payment is made as modelled.

How to Read and Use the Results

Use the monthly payment as the modelled recurring principal-and-interest amount, not as a complete estimate of every amount that may be due. A mortgage payment, for instance, may involve separately billed or collected items such as taxes and insurance; this calculator has no inputs for them. The total interest is the sum implied by the fixed-rate schedule and rounded payment.

An APR is an annualized rate used to describe borrowing costs, but this calculator treats it as a nominal annual rate divided by 12 to obtain a monthly rate. It does not add fees to the principal or model the effect of a fee-based APR calculation. For a specific loan, check the lender’s disclosure for the contractual rate, payment schedule, fees, and exact totals.

The tool gives a payment and interest total rather than a downloadable, row-by-row amortization table. To estimate a balance after k payments, the standard fixed-rate balance formula is P(1 + r)^k − Payment × [(1 + r)^k − 1] ÷ r. Here k is the number of completed monthly payments; the formula assumes the same rate and payment throughout and does not account for irregular timing or extra payments.

Common Misunderstandings and Limits

• APR is not entered as a decimal. Enter 8 for 8%, not 0.08; the formula divides the percentage by 1,200.
• Term means years here. A five-year term corresponds to 60 monthly payments, not five payments.
• Interest is not a fixed share of every payment. Its amount changes as the balance falls, even when the scheduled payment stays level.
• Total interest is not total paid. The total paid is monthly payment × number of payments; subtracting the original principal gives the modelled interest.
• Rounding and timing matter. The calculator rounds the payment to cents. Actual schedules can differ due to payment dates, daily accrual, a final adjusted payment, fees, or variable rates.

The standard formula assumes a positive APR, a fully amortizing loan, equal monthly periods, and a payment that is made as scheduled. It does not model a balloon payment, an introductory rate that later changes, interest-only periods, skipped payments, or additional principal payments. Those features require a schedule that reflects the contract’s specific terms.

Frequently Asked Questions

What does an APR amortization table show?
It lays out how scheduled payments are allocated to interest and principal, along with the remaining balance after each payment. This calculator provides the fixed-rate payment and total-interest summary.

How do I calculate the interest in one monthly row?
Multiply the balance at the start of that month by the monthly rate, APR ÷ 1,200. Subtract that interest from the payment to estimate the principal paid in that row.

Does this calculator include fees or taxes?
No. Fees, taxes, insurance, PMI, and escrow are excluded. The actual lender payment or amount financed may reflect details this estimate does not model.

Why does the last payment sometimes differ?
Cent rounding, payment timing, and how interest accrues can leave a small balance or overpayment near the end. A lender’s schedule may adjust the final amount to settle the balance.

Can I use this for a variable-rate loan?
Only as a simplified estimate for a period with a known, constant rate. It does not project future rate changes or recalculate payments under a variable-rate contract.

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

Related

• Amortization Table Definition and How to Read One
• Amortization Table Calculator in Excel: Formulas
• Free Amortization Table Calculator: Payments and Balance

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 | $ | round(p * (apr / 1200) / (1 - (1 + apr / 1200) ^ -(yrs * 12)), 2) | 2
out int | Total interest | $ | pmt * yrs * 12 - p | 2