Loan Repayment Amortization Schedule Calculator

A loan repayment amortization schedule shows how each regular payment is divided between interest and principal, and how the remaining balance changes over time. Enter the loan amount, annual APR, and term to estimate the monthly payment and total interest; the calculations below use a fixed rate and monthly payments.

Formula

For a fixed-rate loan with equal monthly payments, the payment is calculated using the standard amortizing-loan formula:

Payment = P × r ÷ [1 − (1 + r)⁻ⁿ]

• P is the starting principal, or loan amount, in dollars.
• r is the monthly interest rate as a decimal: APR ÷ 12 ÷ 100. In the calculator, this is apr ÷ 1200.
• n is the number of monthly payments: loan term in years × 12.

The monthly payment is rounded to the nearest cent. Estimated total interest is the rounded monthly payment multiplied by the number of payments, less the original principal: total interest = payment × n − P. This method assumes the same payment is made each month. A real lender’s final payment may differ slightly because of payment dates, rounding, or contract terms.

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 number of payments is 5 × 12 = 60.

Substitute those values into the payment formula:

Payment = 20,000 × 0.0066667 ÷ [1 − (1.0066667)⁻⁶⁰] ≈ $405.53 per month.

Using the displayed, cent-rounded payment, estimated payments over the full term total $405.53 × 60 = $24,331.80. Estimated interest is therefore $24,331.80 − $20,000 = $4,331.80. These totals are mathematical estimates; actual statements can differ if the payment schedule or lender’s rounding differs.

How an Amortization Schedule Works

An amortization schedule is a chronological table of payments. For each period, it shows the payment amount, interest charged, principal repaid, and remaining balance. At the beginning of a typical fully amortizing loan, the balance is larger, so the interest portion is larger. As principal is repaid, less interest accrues in later periods, allowing more of a level payment to go toward principal.

For a monthly schedule, interest for a period is generally calculated on the outstanding balance using the monthly rate. The principal portion is the payment minus that period’s interest. The new balance is the old balance minus principal paid. For example, with a $20,000 balance at 8% APR, the first month’s estimated interest is $20,000 × 0.08 ÷ 12, or about $133.33. From a $405.53 payment, about $272.20 goes to principal, leaving an estimated balance of $19,727.80. Small differences can occur because calculations retain more precision internally than the displayed cents.

How to Read the Results

The monthly payment is the scheduled principal-and-interest amount implied by the entered amount, rate, and term. It is not necessarily the entire monthly bill: mortgages and other loans may have separate taxes, insurance, escrow, or other charges. Total interest is the estimated interest paid over all scheduled payments, assuming the loan runs to the end without changes.

A full schedule makes the progression visible. It can help answer questions such as how much principal remains after a particular payment, or how much interest is charged early in the term. The calculator here reports the payment and estimated total interest rather than listing every period. A separate schedule can be constructed by repeating the interest, principal, and balance steps for each month.

Common Mistakes and Limits

• Entering the wrong rate unit: APR is entered as a yearly percentage, such as 8, not as 0.08 or as a monthly percentage. The formula converts it to a monthly rate.
• Confusing term and payment count: A five-year term means 60 monthly payments, not five payments.
• Assuming APR describes every charge: The calculator uses the entered APR as a rate for the payment calculation. It does not separately model fees or the way a particular lender presents a rate.
• Expecting every loan to amortize evenly: Variable rates, interest-only periods, balloon payments, skipped or irregular payments, and changing payment amounts do not follow this simple fixed-payment schedule.
• Ignoring rounding: A lender may round interest each period or adjust the last payment. Multiplying a rounded estimate by the payment count can therefore differ from an official payoff or account total.

Extra payments can reduce principal sooner and may reduce later interest, but the effect depends on when they are credited and how the contract applies them. This calculator does not include extra payments, missed payments, fees, or changes to the interest rate. For an accurate balance or payoff amount on an existing loan, use the lender’s current account figures and payment history.

Assumptions

• The interest rate is fixed for the whole term.
• Payments are equal and made monthly, with the first payment one month after the loan begins.
• Interest is treated as compounding monthly at APR ÷ 12.
• Fees, taxes, insurance, PMI, escrow, extra payments, and late charges are not included.

Frequently Asked Questions

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

Why does more of my payment go to interest at first?
Interest is calculated on the outstanding balance. That balance is usually highest at the start, so the early interest charge is larger; as principal falls, the interest portion generally falls too.

Does the monthly payment include taxes and insurance?
No. The estimate covers scheduled principal and interest only. Some loan bills include separate charges, which are not represented by this calculation.

Is APR the same as the monthly interest rate?
No. APR is entered as a yearly percentage here. The formula converts it to a monthly rate by dividing the percentage by 1,200.

Why might my lender’s schedule differ from this estimate?
Payment dates, daily interest calculations, rounding, fees, rate changes, and contract-specific payment rules can affect actual figures. Check the lender’s statement or disclosure for the loan’s exact terms.

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

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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