Sample Amortization Schedule: Monthly Loan Breakdown

A sample amortization schedule shows how each loan payment is divided between interest and principal, and how the balance falls over time. Enter a loan amount, APR, and term to estimate the monthly payment, total interest, and a month-by-month schedule using the rounded payment.

Formula

The calculator uses a fixed-payment amortization formula. It first finds the monthly payment, then estimates total interest by subtracting the original principal from all scheduled payments.

• Monthly payment: M = round(P × r ÷ [1 − (1 + r)⁻ⁿ], 2)
• Total interest: I = M × n − P
• Monthly rate: r = APR ÷ 1,200
• Number of payments: n = years × 12

P is the amount borrowed in dollars, APR is the annual percentage rate entered as a percentage, r is the monthly rate as a decimal, n is the number of monthly payments, M is the monthly payment in dollars rounded to cents, and I is estimated total interest in dollars. Because the payment is rounded before total interest is calculated, the displayed total reflects that rounded payment.

Worked Example

Using the defaults—$20,000 principal, 8% APR, and a five-year term—the number of payments is 5 × 12 = 60. The monthly rate is 8 ÷ 1,200 = 0.0066667.

1. Calculate the payment: 20,000 × 0.0066667 ÷ [1 − (1.0066667)⁻⁶⁰] = $405.53 after rounding to cents.
2. Calculate scheduled payments: $405.53 × 60 = $24,331.80.
3. Subtract principal: $24,331.80 − $20,000 = $4,331.80 estimated total interest.

The schedule below illustrates the first three payments and the final payment. Each month, interest is calculated on the balance before payment; the rest of the payment reduces principal. Values are rounded to cents, so a lender’s actual final payment can differ slightly.

Payment	Starting balance	Payment	Interest	Principal paid	Ending balance
1	$20,000.00	$405.53	$133.33	$272.20	$19,727.80
2	$19,727.80	$405.53	$131.52	$274.01	$19,453.79
3	$19,453.79	$405.53	$129.69	$275.84	$19,177.95
60	About $402.85	About $405.53	About $2.69	About $402.84	$0.00

The final-row figures are approximate because the schedule applies monthly rounding; the final payment may be adjusted to clear the remaining balance. The formula’s total-interest output uses the fixed rounded payment for all 60 periods, rather than an adjusted final payment.

Assumptions

• The interest rate remains fixed for the full term.
• Payments are made monthly, at the end of each period.
• Interest compounds monthly at APR ÷ 12; this calculation does not model a lender’s alternative day-count method.
• Fees, taxes, insurance, PMI, escrow, missed payments, and extra principal payments are excluded.

How to Read an Amortization Schedule

A full schedule has one row per payment. The starting balance is the amount still owed before that payment. Monthly interest is approximately the starting balance multiplied by the monthly rate. The payment first covers that interest; the remainder reduces principal. The ending balance becomes the next row’s starting balance.

Early in a level-payment loan, the balance is relatively high, so more of the payment goes to interest. As principal falls, the interest portion generally shrinks and the principal portion grows. This does not mean the payment itself is changing: with the assumptions above, it stays level except for possible rounding or a final adjustment.

What Changes the Schedule

• Principal: A larger starting balance increases the payment and, with the same rate and term, usually increases total interest.
• APR: The APR is an input, not a prediction. Use the rate specified in the loan documents when available.
• Term: A longer term spreads repayment across more months. It changes both the scheduled payment and total interest.
• Extra payments: Additional amounts applied to principal can change later balances and interest, but this calculator does not model them.
• Payment timing and rounding: Actual accrual may depend on dates and lender methods; rounding each month can create small differences.

A schedule is useful for understanding planned principal reduction and checking how a fixed-payment calculation works. It is not necessarily a payoff quote: an exact payoff amount can depend on interest accrued through a particular date, payment posting, fees, or other contract details.

Common Misconceptions and Limits

Total interest here means scheduled payments minus principal under the stated assumptions. It is not the same as APR: APR is a rate measure, while total interest is a dollar estimate over the modeled term. The calculation also does not add fees to the balance or include taxes, insurance, or escrow in the monthly payment.

Do not treat the table’s cents as a promise of an exact lender ledger. The example rounds displayed amounts, while real servicing can use payment dates, daily interest accrual, and adjustments. Variable rates, irregular payments, deferments, and missed payments require a different schedule. For those situations, use the actual payment terms and a method that models the relevant changes.

Frequently Asked Questions

What does an amortization schedule show?
It shows each scheduled payment split into interest and principal, along with the remaining loan balance after each payment.

Why does the interest portion decrease over time?
With a fixed rate, interest is calculated on the outstanding balance. As principal is repaid, the balance falls, so the interest charged per period generally falls too.

Does this calculator create a full monthly table?
It estimates the level monthly payment and total interest. The sample table illustrates how rows work; the formula block does not output every month as a separate result.

Is total interest the same as APR?
No. APR is an annual rate input. Total interest is an estimated dollar amount across the modeled payments and term.

Why might my lender’s schedule differ?
Differences can result from payment dates, daily accrual, rounding, fees, a variable rate, or an adjusted final payment. Compare the assumptions and use the lender’s disclosure for contract figures.

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

Related

• Amortization Schedule: Principal and Interest
• Amortization Schedule Ramsey: How Loan Payments Break Down
• Amortization Schedule Calculator and Loan Payment Breakdown

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