Loan Calculator Repayment Schedule and Monthly Breakdown

A loan calculator repayment schedule shows how each scheduled payment is divided between interest and principal, and how the balance changes over time. Enter the loan amount, annual percentage rate (APR), and term to estimate the monthly payment and total interest; this calculator provides those summary figures, while the schedule method below explains how to build the month-by-month breakdown.

Formula

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

Monthly payment = P × r ÷ [1 − (1 + r)⁻ⁿ]

• P is the amount borrowed, in dollars.
• r is the monthly interest rate as a decimal: APR ÷ 12 ÷ 100. In the calculator expression this is APR ÷ 1200.
• n is the number of monthly payments: loan term in years × 12.
• APR is the annual percentage rate entered as a percentage, not a decimal.

The calculator rounds the monthly payment to the nearest cent. Total interest is estimated as the rounded monthly payment multiplied by the number of months, minus the original loan amount. Because an actual final payment may be adjusted to clear the remaining balance, the displayed total is an estimate based on equal rounded payments.

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 formula: $20,000 × 0.0066667 ÷ [1 − (1.0066667)⁻⁶⁰].
4. The result is approximately $405.53 per month, rounded to cents.
5. Estimated total interest: $405.53 × 60 − $20,000 = $4,331.80.

The schedule method below shows how that payment is allocated. Small differences can arise from rounding each month’s interest and from a lender adjusting the last payment.

Assumptions

• The interest rate stays fixed for the entire term.
• Payments are equal, made monthly, and paid at the end of each monthly period.
• Interest compounds monthly using APR divided by 12.
• Fees, taxes, insurance, PMI, escrow, and changes to payment timing are not included.

How a Repayment Schedule Works

At the start of each period, interest accrues on the outstanding balance. The interest portion of that month’s payment is the balance multiplied by the monthly rate. The remainder reduces principal:

• Monthly interest = opening balance × monthly rate.
• Principal repaid = scheduled payment − monthly interest.
• Closing balance = opening balance − principal repaid.

For the example, the first month’s interest is $20,000 × 0.0066667, or about $133.33. Of the $405.53 payment, about $272.20 therefore reduces principal, leaving an estimated balance of $19,727.80. In the next month, interest is calculated on that lower balance. As a result, the interest share generally declines over time while the principal share rises.

A schedule table typically has columns for payment number or date, opening balance, payment, interest, principal, and closing balance. To create a month-by-month estimate, repeat the calculations using each month’s closing balance as the next month’s opening balance. Round consistently to cents if matching a lender statement; rounding can cause a small difference in the final balance.

How to Read and Use the Results

The monthly payment is the estimated level amount needed to repay principal and interest over the entered term under the stated assumptions. Total interest represents the estimated borrowing cost from interest alone across the full scheduled term; it is not the total of every possible loan charge.

A schedule can help answer practical arithmetic questions, such as how much principal is expected to remain after a given number of payments or how payments are allocated early versus later. Compare the calculator inputs with the lender’s disclosure: the amount financed, rate, term, payment frequency, and any fees can change the actual figures. Enter the rate as an annual percentage—for example, 8 for 8%, not 0.08—and enter the term in years, not months.

Common Schedule Mistakes and Limits

• Confusing APR and the monthly rate: For this formula, enter APR as a percent and divide by 1200 to get a monthly decimal rate.
• Assuming the payment includes every housing or borrowing cost: This calculation covers principal and interest only. Other charges may be billed separately or handled differently.
• Ignoring variable rates or irregular payments: A fixed-rate, level-payment schedule will not reproduce a loan whose rate, payment date, or payment amount changes.
• Expecting every statement to match to the cent: Daily interest, payment posting dates, rounding practices, fees, and a final-payment adjustment can affect a lender’s figures.

The formula is not a substitute for a lender’s account-level payoff figure. It also does not model late payments, skipped payments, extra principal, fees added to the balance, or changes in interest rates. To estimate an extra-payment plan, the balance must be recalculated period by period using the revised payment amounts and the loan’s actual interest rules.

Frequently Asked Questions

What is a loan repayment schedule?
A repayment schedule is a sequence of planned payments showing how much goes to interest and principal and what balance remains after each payment.

Why does more of an early payment go to interest?
Interest is calculated on the outstanding balance. At the beginning, the balance is larger, so the interest charge takes a larger share of a level payment. As principal is repaid, that charge generally falls.

Does the calculator’s total interest include fees?
No. The estimate uses the entered principal, APR, and term. Fees and other charges are excluded unless they are represented in the inputs or included in the lender’s rate calculation.

Can I use this schedule for a variable-rate loan?
Only as a snapshot under the entered rate. If the rate changes, the payment or payoff timeline may change too, so a single fixed-rate schedule cannot represent future adjustments.

Why might my lender’s final payment differ?
Monthly rounding, daily interest calculations, posting dates, fees, or other contract details can change the balance slightly. The lender’s current payoff or payment information accounts for its records and terms.

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

Related

• Loan Repayment Schedule Calculator and Payment Breakdown
• 10-Year Business Loan Repayment Schedule Calculator
• 20 Year Student Loan Repayment Schedule Calculator

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