Loan Payment Example: Monthly Payment and Total Cost

A loan payment example shows how a fixed-rate loan’s amount, annual percentage rate (APR), and term determine its monthly payment and total interest. Enter those three figures to estimate the payment and interest over the full term; the example below uses a $20,000 loan at 8% APR for five years.

Formula

For a fixed-rate loan repaid in equal monthly payments, the standard amortization formula is:

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

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

Total interest in this calculator is monthly payment × number of payments − principal. It uses the payment rounded to cents, so the interest estimate follows the displayed monthly amount. Real loan schedules may adjust the final payment to settle a small remaining balance.

Worked Example

Using the calculator’s default inputs—$20,000 principal, 8% APR, and a five-year term:

1. Convert the APR to a monthly decimal rate: 8 ÷ 12 ÷ 100 = 0.0066667, or about 0.66667% per month.
2. Find the number of payments: 5 × 12 = 60.
3. Substitute in the formula: $20,000 × 0.0066667 ÷ [1 − (1.0066667)⁻⁶⁰].
4. The unrounded payment is about $405.53; rounded to cents, the monthly payment is $405.53.
5. Calculate total payments using the rounded payment: $405.53 × 60 = $24,331.80. Subtract the $20,000 principal: estimated total interest is $4,331.80.

Assumptions

• The interest rate stays fixed throughout the term.
• Payments are equal, made monthly, and paid at the end of each monthly period.
• Interest compounds monthly at APR divided by 12.
• The calculation excludes fees, taxes, insurance, PMI, and escrow, as well as any payment changes or extra payments.

How to Read a Loan Payment

The monthly payment combines interest and principal. Early in a fully amortizing loan, the balance is larger, so more of each payment goes toward interest. As the balance falls, the interest portion generally declines and more of the payment reduces principal. The payment formula accounts for this changing split while keeping the scheduled payment level.

The total-interest result is the estimated interest across all scheduled payments, not the total amount borrowed and not the monthly cost of owning an asset. For the example, the scheduled payments add up to $24,331.80: $20,000 repays principal and $4,331.80 is estimated interest. This distinction helps answer a common question: a $405.53 payment does not mean the loan costs only $405.53 overall.

What Changes the Payment?

• Principal: With the APR and term unchanged, borrowing more increases the payment and total interest.
• APR: A higher APR raises the amount of interest charged and generally increases the payment for the same term and principal. Enter the rate quoted for the loan; the calculator does not determine what rate applies.
• Term: Spreading repayment over more months generally lowers each scheduled payment, but can increase total interest because interest accrues for longer.

These relationships describe the formula, not a judgment about which loan or term someone should choose. Actual rates and charges depend on the specific loan documents. Get the applicable figures from the lender’s disclosure rather than treating the example’s 8% APR as a current or typical rate.

When This Estimate Helps—and Its Limits

This calculation can help with an initial comparison of payment amounts when the principal, APR, and term are known. It can also show how a change in one input affects the arithmetic while the other inputs remain fixed. For an apples-to-apples calculation, use the same assumptions about what the stated rate includes and how payments are scheduled.

A standard fixed-payment calculation may not match a loan with a variable rate, interest-only period, balloon payment, irregular payment dates, deferred interest, or fees added to the balance. It does not calculate an APR from fees or model lender-specific rounding and payment allocation. APR is an input here; the calculator does not verify whether a quoted APR captures every charge relevant to a particular loan.

Taxes, insurance, PMI, escrow, and other recurring costs are not part of the principal-and-interest payment shown. If a lender collects any of these alongside a payment, the amount due may differ from this estimate. Extra payments can also change payoff timing and interest, but they are not included in this calculation.

Common Calculation Mistakes

• Entering 8 instead of 0.08 in a different formula: This calculator accepts APR as a percentage, so enter 8 for 8%. Its formula converts that value to a monthly decimal rate.
• Using years as payment count: The term input is in years, and the formula multiplies it by 12 to get monthly payments.
• Comparing payment with total cost: A monthly amount alone does not show total interest. Review the term and the total-interest result as well.
• Assuming every quoted payment includes all costs: Confirm whether the lender’s figure includes fees or other recurring charges; this calculator does not.
• Rounding intermediate values too early: The worked example keeps the formula’s precision until the payment is rounded to cents. Small differences can arise if a lender uses a different schedule or final-payment adjustment.

Frequently Asked Questions

How much is the monthly payment on a $20,000 loan?
It depends on the APR and repayment term. At the example inputs of 8% APR and five years, the estimated monthly principal-and-interest payment is $405.53.

Does a loan payment include interest?
In a standard amortizing loan, each scheduled payment includes both interest and principal. The share going to each changes as the balance is repaid.

Why is the total interest more than the first month’s interest?
Total interest adds the interest charged across every payment period. The first month’s interest is only one part of that full repayment schedule.

Does a longer loan term lower the payment?
For the same principal and APR, a longer term generally spreads repayment across more payments and reduces the scheduled amount per month. It can also increase total interest because the balance remains outstanding longer.

Is this the exact amount a lender will charge?
No. The estimate uses a fixed rate and simplified monthly schedule and excludes fees and other costs. The lender’s disclosure gives the exact figures for the loan.

This result is an estimate, and 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 | $ | p * (apr / 1200) / (1 - (1 + apr / 1200) ^ -(yrs * 12)) | 2
out int | Total interest | $ | pmt * yrs * 12 - p | 2