Loan Repayment Schedule Calculator and Example

Generate a loan repayment schedule by entering the loan amount, annual percentage rate (APR), and term. This calculator estimates the fixed monthly payment and total interest; the schedule explains how each payment is divided between interest and principal over time.

Formula

This calculator uses the standard fixed-payment amortization formula. It assumes payments are monthly and the monthly interest rate is the annual APR divided by 12:

• Monthly payment: M = round[P × r ÷ (1 − (1 + r)⁻ⁿ), 2]
• Total interest: I = (M × n) − P

Here, P is the starting loan principal in dollars, apr is the annual percentage rate in percent, r = apr ÷ 1200 is the monthly rate as a decimal, n is the number of monthly payments (years × 12), M is the payment in dollars rounded to cents, and I is estimated total interest in dollars. The total uses the rounded monthly payment, as actual payments are normally made in currency units. The final payment may differ slightly if a lender adjusts it to clear a remaining balance.

Worked Example

Using the calculator’s defaults: a $20,000 principal, 8% APR, and a 5-year term.

1. Convert APR to a monthly rate: 8 ÷ 1200 = 0.0066667.
2. Find the number of payments: 5 × 12 = 60.
3. Apply the payment formula: $20,000 × 0.0066667 ÷ [1 − (1 + 0.0066667)⁻⁶⁰] = $405.53, rounded to cents.
4. Calculate total interest using that rounded payment: ($405.53 × 60) − $20,000 = $4,331.80.

The results are an estimated monthly payment of $405.53 and estimated total interest of $4,331.80. Because the payment is rounded each month, a real lender’s final payment and total may vary by a few cents.

Assumptions

• The rate stays fixed for the full loan term.
• Payments are equal, made monthly, and applied at the end of each monthly period.
• Interest compounds monthly at APR ÷ 12.
• The calculation excludes fees, taxes, insurance, PMI, escrow, missed payments, and extra payments.

How a Repayment Schedule Works

A repayment schedule, also called an amortization schedule, lays out the expected payment-by-payment change in the loan balance. For each period, interest is calculated on the outstanding principal. The rest of the payment reduces principal. As the balance falls, the interest portion generally shrinks and the principal portion grows, even though the scheduled payment remains level.

For a detailed row, a basic monthly calculation is: interest for the month = opening balance × monthly rate; principal paid = monthly payment − interest; closing balance = opening balance − principal paid. For example, on the default loan, the first month’s estimated interest is $20,000 × 0.0066667, or about $133.33. Of the $405.53 payment, about $272.20 then reduces principal, leaving an estimated $19,727.80 balance. Small differences can result from rounding and lender-specific posting practices.

When to Use the Estimate

Use a repayment calculation to understand the basic payment pattern or to check how a change in principal, APR, or term affects the arithmetic. It can help you prepare questions about a loan quote and see why a longer term generally spreads principal repayment across more months, while interest continues to accrue on the unpaid balance. This is a mathematical comparison, not a recommendation about borrowing or choosing a particular loan.

Enter the loan’s principal rather than the total of all scheduled payments. Use the annual rate in percent, such as 8 for 8%, not 0.08. Enter a term in years; the calculator converts it to months. APR can include certain borrowing costs depending on how it is disclosed, but this calculation treats the entered APR as the rate used for monthly interest and does not separately model charges.

Reading the Results and Limits

The monthly payment is the estimated regular amount needed to repay principal and interest over the stated term under the formula’s assumptions. Total interest is the sum of those rounded payments minus the original principal. It is not the total amount paid: estimated principal plus interest equals $24,331.80 in the worked example.

A complete schedule contains one row for each payment date, with opening balance, payment, interest, principal repaid, and closing balance. The calculator summarizes the payment and interest rather than listing all rows. A schedule from a lender can differ when it uses daily interest, a variable rate, a first payment period of unusual length, payment dates that shift, fees added to the balance, or a different rounding method. Extra principal payments also change later interest and payoff timing, so they are not represented here.

One common misconception is that every month’s payment reduces principal by the same amount. With a level-payment, fixed-rate loan, the payment is usually steady, but its principal and interest components change over time. Another is that total interest can be calculated from an unrounded payment: this calculator instead uses the displayed cent-rounded payment, making the worked total consistent with its stated assumptions.

Common Inputs and Problems

• Check the balance: Use the amount actually financed. If charges are financed, the starting principal may be higher than the amount received.
• Check the rate basis: APR is entered as a yearly percentage. Do not enter a monthly rate in the APR field.
• Check the term: A 5-year term means 60 monthly payments, not five payments.
• Watch for changing terms: A variable rate or an introductory rate that later changes cannot be represented by one fixed APR.
• Compare like with like: Ensure figures use the same principal, rate basis, term, and included charges before interpreting differences.

If a lender provides a payment or amortization table, use its disclosed figures for the actual contract. Ask how the lender handles payment allocation, rate changes, fees, and any final adjustment if those details affect the schedule.

Frequently Asked Questions

How do I generate a loan repayment schedule?
Enter the principal, annual APR, and term. Calculate the monthly payment, then for every month calculate interest on the opening balance, subtract that interest from the payment to find principal repaid, and subtract principal repaid from the balance.

Does this calculator show every payment date?
No. It estimates the fixed monthly payment and total interest. A full schedule requires one calculation per payment period and the actual payment dates and lender rules.

Why does the principal portion increase over time?
With a fixed rate and level payment, interest is charged on the remaining balance. As principal is repaid, the balance and monthly interest generally decline, leaving more of the same payment to reduce principal.

Does APR include all loan costs?
Not necessarily in a way this calculation can reproduce. The calculator does not add fees or other charges as separate items. Use the lender’s disclosed payment and cost figures for the specific loan.

Why might my lender’s schedule be different?
Differences can arise from daily rather than monthly interest, payment timing, variable rates, fees, rounding, or an adjusted last payment. The calculation is an estimate and the lender’s disclosure gives the exact figures.

Related

• U.S. Bank Personal Loan APR and Payment Calculator
• UR Loan Application: Payment Calculator and Guide
• US Bank Auto Loan Payoff Address and Payment Options

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