calculate-loan

01 Loan payments

APR Calculator: Estimate Monthly Payment and Total Interest

Calculator No. 01-6035 · Updated · Formula and assumptions shown below

Monthly payment $405.53
Total interest
$4,331.80
= Monthly payment × loan term × 12 − loan amount
Loan amount
$20,000
Input
Interest rate (APR)
8 %
Input
You enter
Loan amount ($), Interest rate (APR) (%), Loan term (years)
You get
Monthly payment ($), Total interest ($)
Rounding
2 dp

Estimate for education, not financial advice. The result follows from the numbers you enter and the formula shown. It is not a quote or an offer, and it does not include fees, taxes or insurance unless the calculator asks for them. Ask your lender for the exact figures.

An APR calculator estimates a fixed-rate loan’s monthly payment and total interest from the loan amount, annual percentage rate, and term. Enter those three figures to see the estimated payment and the interest paid over the full term, assuming on-time monthly payments and no added fees.

Formula

The calculator uses the standard level-payment formula for a fixed-rate loan, with monthly payments and the monthly rate set to APR divided by 12:

Monthly payment = round[P × r ÷ (1 − (1 + r)−n), 2]

Total interest = monthly payment × n − P

  • P is the loan amount in dollars.
  • APR is the annual percentage rate entered as a percentage, such as 8 for 8% per year.
  • r is the monthly rate as a decimal: APR ÷ 1,200.
  • n is the number of monthly payments: loan term in years × 12.
  • Monthly payment is rounded to the nearest cent before the total interest is calculated.

APR can reflect certain borrowing costs as well as interest, depending on how the lender calculates and discloses it. This calculator treats the entered APR as a fixed annual rate applied monthly. It does not separately model any fee or how that fee is charged. Use the lender’s disclosed figures for a loan-specific estimate.

Worked Example

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

  1. Convert the APR to a monthly decimal rate: 8 ÷ 1,200 = 0.0066667.
  2. Convert the term to payments: 5 × 12 = 60 monthly payments.
  3. Apply the payment formula: $20,000 × 0.0066667 ÷ [1 − (1.0066667)−60] = $405.53 when rounded to cents.
  4. Calculate total interest using the rounded payment: $405.53 × 60 − $20,000 = $4,331.80.

The estimated monthly payment is $405.53, and total interest across the scheduled payments is $4,331.80. The payment multiplied by 60 is $24,331.80, consisting of the $20,000 principal and $4,331.80 interest.

Assumptions

  • The rate is fixed for the entire term.
  • Payments are equal, made monthly, and paid at the end of each monthly period.
  • Interest is modelled monthly at APR ÷ 12.
  • There are no extra payments, late payments, or changes to the schedule.
  • Fees, taxes, insurance, PMI, and escrow are not separately included.

When to Use an APR Calculator

Use this estimate to understand how the loan amount, rate, and repayment period affect a regular payment and the overall interest cost. It can also help you check the arithmetic on a quoted fixed-payment schedule. Enter the APR and term supplied for the specific loan; the default values are only an example, not a statement about available rates or terms.

APR and interest rate are related but are not always interchangeable. The interest rate is the cost used to calculate interest on the outstanding balance. APR is a broader disclosure measure that may incorporate certain fees, so it can differ from the stated interest rate. Lender methods and the treatment of charges matter. This calculator does not infer fees from APR or reproduce every lender’s disclosure method.

For a variable-rate loan, the payment may change when the rate changes, so a single fixed-rate calculation cannot show the full future schedule. For an interest-only loan, a balloon loan, or a loan with irregular payments, the level-payment formula may not describe the contract. Check the payment structure and assumptions before interpreting the result.

How to Read the Results

The monthly payment is the scheduled principal-and-interest amount under the model. Early payments on an amortizing loan generally allocate a larger share to interest; later payments allocate more to principal, because interest is calculated on a declining balance. The total interest figure is the sum implied by the rounded monthly payment over the entered number of months. It is not the total amount of every possible loan-related charge.

A longer term generally spreads repayment over more months and changes both the payment and the accumulated interest. A different APR also changes the payment and the interest portion. These are mathematical effects, not a determination of whether a particular loan fits a person’s circumstances.

Common Errors and Calculator Limits

  • Entering a decimal instead of a percentage: Enter 8 for 8% APR, not 0.08. The formula converts the percentage to a monthly decimal.
  • Mixing annual and monthly terms: Enter the term in years. The calculator multiplies it by 12 to get the payment count.
  • Using an amount different from the amount financed: A quoted loan amount may exclude a fee or include charges financed into the balance. Use the figure that matches the calculation you want.
  • Ignoring rounding: The monthly payment is rounded to cents before total interest is computed. A lender’s payment schedule may differ slightly due to rounding conventions, dates, or its fee treatment.
  • Treating the estimate as an offer: The calculator does not establish eligibility, approval, a final rate, or the exact terms of a contract.

The APR input must be at least 0.01% because the payment formula divides by a positive rate. The loan amount and term must also be positive. This model is for a standard, fully amortizing loan with equal monthly payments; it does not calculate payoff amounts on a particular date or account for extra payments.

Frequently Asked Questions

How much will my monthly payment be?
Enter the loan amount, APR, and term. The calculator estimates the fixed monthly payment using the standard amortizing-loan formula and rounds it to cents.

Is APR the same as the interest rate?
No. APR is a broader borrowing-cost measure and may include certain fees, while the interest rate is used to calculate interest on the balance. Their exact relationship depends on the loan’s terms and disclosure.

Does the total interest include fees?
No. The displayed total is derived from the rounded monthly payment and principal in this formula. Fees and other charges are not entered or separately itemized.

Why does a lender’s payment differ from this result?
Possible reasons include a different amount financed, rate, term, payment date convention, fee treatment, or rounding method. Compare the calculator inputs with the lender’s written payment schedule.

Can I use this for a variable-rate loan?
Only as a snapshot based on the APR entered. If the rate changes, the payment or repayment schedule may change, and this fixed-rate calculation does not project those changes.

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

Related

Formula used
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

Each line is one input (in, sel, list) or one result (out: label, unit, formula, decimals). How the calculators work

Method: the standard loan formula for this calculation, fixed rate and monthly compounding unless stated, rounded as each result states. Not financial advice; no lender, rate or product is recommended. See formulas and assumptions, the disclaimer or report an error.

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