Monthly Payment Plan? Calculate a Loan Payment

This monthly payment calculator estimates the level payment needed to repay a fixed-rate loan over a set term. Enter the loan amount, annual percentage rate (APR), and term in years to see the monthly payment and estimated total interest.

Formula

For a fixed-rate loan repaid in equal monthly installments, the payment is calculated with the standard amortization formula:

PMT = P × r / [1 − (1 + r)−n]

• PMT is the monthly payment, in dollars.
• P is the amount borrowed, in dollars.
• r is the monthly interest rate as a decimal, calculated here as APR ÷ 1,200. For an 8% APR, r is 8 ÷ 1,200.
• n is the number of monthly payments, calculated as years × 12.

The calculator’s total-interest estimate is PMT × n − P. It uses the displayed monthly payment rounded to the nearest cent, so the total is consistent with that rounded payment. A lender’s actual final payment may differ because of rounding, payment dates, fees, or contract terms.

Worked Example

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

1. Convert the APR to a monthly decimal rate: r = 8 ÷ 1,200 = 0.0066667 (approximately).
2. Find the number of payments: n = 5 × 12 = 60.
3. Substitute into the payment formula: PMT = 20,000 × 0.0066667 ÷ [1 − (1.0066667)−60].
4. Round the result to cents: the estimated monthly payment is $405.53.
5. Estimate total interest using the rounded payment: $405.53 × 60 − $20,000 = $4,331.80.

The payment and interest are estimates under the stated assumptions. Calculations done with unrounded intermediate values can produce a slightly different displayed figure before cent rounding.

Assumptions

• The interest rate stays fixed for the full term.
• Payments are equal, made monthly, and occur at the end of each monthly period.
• Interest is modelled monthly at APR divided by 12.
• The calculation excludes fees, taxes, insurance, PMI, and escrow; none are inputs in this calculator.

How to Use the Monthly Payment Estimate

Enter the principal—the amount borrowed, not necessarily the total purchase price—along with the APR and the repayment term in years. The calculator returns a level monthly principal-and-interest payment and an estimate of interest over the entire scheduled term. If the lender quotes the term in months, divide that number by 12 before entering it; for example, 48 months is 4 years.

Use the APR supplied for the specific loan offer when you have it. The default 8% is only an example input, not a statement about current or typical borrowing costs. If the quoted rate is variable, a single fixed-rate estimate cannot show how later rate changes would affect payments. Get the applicable rate, fees, and payment schedule from the lender’s documents.

The payment is not necessarily the complete amount due each month. A mortgage payment, for instance, may include items such as taxes or insurance collected with the loan payment. Other loans may have fees or a different schedule. Since this calculator has no inputs for those amounts, compare its principal-and-interest estimate only with the matching part of a lender’s quoted payment.

What Changes the Payment?

For a given rate and term, borrowing more increases the monthly payment. A higher APR also raises the payment. Extending the term generally lowers the required monthly payment in this fixed-rate model, while increasing the number of payments over which interest accrues. As a result, a lower monthly amount does not by itself mean the loan costs less overall.

For example, when considering the same principal and APR across two terms, the shorter term has fewer scheduled payments and generally a larger monthly installment; the longer term spreads repayment over more months. The calculator can illustrate that arithmetic by changing the term while holding the other inputs constant. It does not account for whether a borrower qualifies or what payment is appropriate for their circumstances.

Interest is not calculated as a simple one-time percentage of the original principal for the whole term. In an amortizing loan, each payment covers interest accrued for the period and reduces the balance with what remains. Early payments usually devote a larger share to interest because the outstanding balance is higher; later payments devote more to reducing principal, assuming the rate and payment remain unchanged.

Common Mistakes and Limits

• Entering a monthly rate as an APR: enter the annual rate as a percentage, such as 8 for 8%. The formula converts it to a monthly rate.
• Confusing term units: this calculator asks for years, not months. Entering 60 for a 60-month loan would mean 60 years.
• Using the purchase price instead of the loan amount: subtract any down payment or other amount not financed before entering the principal.
• Treating the estimate as a quote: payment dates, daily-interest methods, fees, variable rates, and final-payment adjustments can make a contractual schedule differ.
• Assuming all costs are included: the result does not include add-on charges, taxes, insurance, or escrow.

The formula assumes the loan is fully repaid through equal payments and that the APR can be represented as a fixed monthly rate of APR divided by 12. It is not designed for interest-only periods, balloon payments, irregular payment intervals, changing rates, or loans with a separate fee-financed balance. APR definitions and contract calculations can also vary by product, so use the lender’s disclosed schedule for exact figures.

Frequently Asked Questions

What does a monthly payment plan mean?
It usually means repaying a balance in scheduled monthly installments. For a standard amortizing loan, each installment covers interest and reduces principal, with the goal of paying off the balance by the end of the term.

Does the monthly payment include interest?
Yes. The estimate includes principal and interest. It does not include fees, taxes, insurance, or other charges unless those are separately built into the loan amount or payment arrangement.

Why does a longer loan term lower the monthly payment?
The same principal is divided across more scheduled payments. In a fixed-rate amortizing loan, interest continues to accrue while the balance remains outstanding, so a longer term can also mean more total interest across the schedule.

Is APR the same as the monthly interest rate?
No. APR is entered as an annual percentage. This calculator divides it by 12 to form a monthly rate, expressed as a decimal inside the formula. Contract details and fees can affect how a lender presents APR.

Why is my lender’s payment different from this result?
The lender may use a different rate, loan amount, payment date, rounding method, or term, or include charges the calculator does not model. Check the loan disclosure and payment schedule for the exact figures.

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