Loan Repayment Schedule Calculator and Payment Breakdown

This loan repayment schedule calculator estimates your monthly payment, total interest, and total of scheduled payments from the loan amount, APR, and term. Enter the figures from a lender’s loan disclosure or a clearly identified example; the results show the level-payment estimate, not a lender-issued account schedule.

Formula

The calculator uses the standard fixed-rate amortizing-loan formula. It assumes a constant monthly payment, with interest accruing monthly at the APR divided by 12:

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

• P is the starting loan principal, in dollars.
• APR is the annual percentage rate entered as a percent per year.
• r is the monthly rate as a decimal: APR ÷ 1200.
• n is the number of monthly payments: loan term in years × 12.
• Payment is the monthly amount, rounded to the nearest cent.

Total scheduled payments equal the rounded monthly payment multiplied by the number of months. Estimated total interest is that total minus the original principal. Because the payment is rounded before totals are calculated, the final payment in an actual loan schedule can differ slightly to settle the remaining balance.

Worked Example

Using the calculator’s defaults: a $20,000 loan, 8% APR, and a five-year term.

1. Convert APR to a monthly decimal rate: 8 ÷ 1200 = 0.0066667.
2. Find the number of payments: 5 × 12 = 60.
3. Substitute into the payment formula: $20,000 × 0.0066667 ÷ [1 − (1.0066667)⁻⁶⁰] = approximately $405.53 per month after rounding.
4. Multiply the rounded payment by 60: $405.53 × 60 = $24,331.80 in scheduled payments.
5. Subtract the principal: $24,331.80 − $20,000 = $4,331.80 in estimated interest.

Assumptions

• The interest rate is fixed for the entire term.
• Payments are equal, made monthly, and applied at regular intervals.
• Interest is modelled monthly at APR ÷ 12; actual loan disclosures may use different day-count or accrual conventions.
• The calculation excludes fees, taxes, insurance, PMI, escrow, and any charges not entered as part of the principal or rate.

How to Read a Repayment Schedule

A repayment schedule, also called an amortization schedule, lists each payment period and shows how the payment is divided between interest and principal. Early in a typical amortizing loan, the outstanding balance is larger, so more of a level payment goes toward interest. As the balance declines, the interest portion usually becomes smaller and the principal portion larger.

For example, at the start of the default calculation, monthly interest on $20,000 at 8% APR is about $133.33 ($20,000 × 0.0066667). Of the estimated $405.53 first payment, roughly $272.20 would reduce principal, before any lender-specific adjustments. The next period’s interest is calculated on the lower balance. The calculator gives summary totals; it does not print every payment row or model a different payment date.

Use the monthly payment to understand the formula’s regular-payment estimate, total scheduled payments to see the sum of those payments, and total interest to isolate the estimated borrowing cost under the stated assumptions. These figures are not a complete measure of every cost associated with a loan.

When the Estimate May Differ

A schedule based on this formula can differ from a lender’s figures if the contract has fees financed into the balance, a variable rate, irregular payment dates, a final adjusted payment, or a different way of calculating accrued interest. A lender may also quote a payment that includes other items, such as insurance or escrow; those are not part of this calculator’s principal-and-interest estimate.

• Check the APR and principal: confirm whether the quoted amount is the amount borrowed or includes financed charges.
• Check the term: enter the number of years over which scheduled monthly payments are due.
• Keep units consistent: APR is entered as a percentage, such as 8, not as 0.08; the calculator converts it to a monthly rate.
• Expect rounding: a lender may round interest each period or adjust the last payment, so exact totals can vary by cents or more.

A common misconception is that APR alone determines the full cost of borrowing. The principal and repayment period also affect the payment and total interest, and costs not included in the APR or calculator inputs may affect what is actually paid. For an exact schedule, use the payment dates, rate terms, and balance rules in the lender’s disclosure.

Extra Payments and Other Schedule Changes

This estimate assumes only the regular level payment. If a borrower pays extra toward principal, the balance may fall faster and the amount of future interest may change, but the outcome depends on how the lender applies the extra amount and whether contract terms or charges affect the schedule. This calculator does not determine those details.

A changed rate or payment amount also requires a different calculation. For a variable-rate loan, a single APR cannot represent every future period. A useful way to compare a calculator result with a statement is to match the starting balance, applicable rate, payment amount, payment frequency, and remaining term for the same date. If those inputs do not align, the outputs should not be expected to match.

Frequently Asked Questions

What is a loan repayment schedule?
A repayment schedule lays out the payments due over a loan term and, typically, the interest and principal portions and remaining balance after each payment. This calculator estimates the payment and totals, rather than displaying every period.

How do I calculate a monthly loan payment?
Use the amortizing-payment formula: principal multiplied by the monthly rate, divided by one minus (one plus the monthly rate) raised to the negative number of payments. Convert APR to a monthly decimal by dividing it by 1200, and round the result to cents.

Does a longer loan term mean less total interest?
Not necessarily. With the same principal and rate, a longer term generally spreads repayment across more payments, while interest continues to accrue on the balance. This calculator shows the estimate for the specific term entered; it does not recommend a term.

Why is my lender’s payment different?
The lender may use a different principal, rate, term, payment date, accrual convention, or rounding method. The quoted payment may also include costs this estimate excludes. Compare the inputs and the lender’s disclosure rather than treating the calculator as an account statement.

Does this calculator include extra payments?
No. It assumes the same regular monthly payment throughout the term and does not model additional principal payments, skipped or late payments, rate changes, or lender-specific handling of payments.

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

Related

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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
out tot | Total scheduled payments | $ | pmt * yrs * 12 | 2