calculate-loan

01 Loan payments

Payment Calculator With Interest Rate: Monthly Cost

Calculator No. 01-5173 · Updated · Formula and assumptions shown below

Monthly payment $405.53
Total interest
$4,331.67
= 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.

A payment calculator with an interest rate estimates the fixed monthly payment on a loan from its amount, annual percentage rate (APR), and term. Enter those three figures to see the monthly payment and total interest; the estimate assumes regular monthly payments and a rate that stays fixed.

Formula

The calculator uses the standard fixed-payment amortization formula. It converts the annual APR to a monthly rate, then finds the payment that repays principal and interest over the selected number of monthly periods:

Payment = P × r ÷ [1 − (1 + r)−n]

  • P is the loan principal, in dollars.
  • r is the monthly interest rate as a decimal: APR ÷ 1,200. For an 8% APR, r = 8 ÷ 1,200.
  • n is the total number of monthly payments: loan term in years × 12.

Total interest is estimated as the monthly payment multiplied by the number of payments, minus the original principal. In symbols, Total interest = payment × n − P. The calculator uses the unrounded payment in that expression and displays both results to the nearest cent. Actual billing schedules may differ slightly if payments are rounded each month.

Worked Example

Using the calculator’s default inputs—$20,000 principal, 8% APR, and a five-year term—the monthly rate is 0.08 ÷ 12 = 0.0066667, and the number of payments is 5 × 12 = 60.

Substitute those values into the payment formula:

Payment = $20,000 × 0.0066667 ÷ [1 − (1.0066667)−60] ≈ $405.53 per month.

Total interest is approximately $405.53 × 60 − $20,000 = $4,331.80. The corresponding total of scheduled payments is about $24,331.80. These figures are estimates; a lender’s payment schedule can differ because it may round each installment or use different timing and calculation conventions.

Assumptions

  • The interest rate is fixed for the entire loan term.
  • Payments are equal, made monthly, with the first payment one month after borrowing.
  • Interest compounds monthly at APR ÷ 12.
  • Fees, taxes, insurance, PMI, escrow, and optional products are not included.

How to Use and Read the Estimate

Enter the amount borrowed—not necessarily the purchase price—the annual APR quoted for the loan, and the term in years. The APR input is a percentage, so enter 8 for 8%, not 0.08. The calculator returns the scheduled principal-and-interest payment and the interest implied by that payment across the full term.

The monthly payment is not the same as the total monthly cost of owning or financing something. A mortgage payment, for example, may be accompanied by property-related charges or insurance; an auto loan may have taxes or other costs outside the loan installment. Since these are not inputs here, add them separately when estimating a full budget. Likewise, any fee added to the amount financed changes the principal and therefore the calculated payment.

The total-interest figure assumes every scheduled payment is made on time and the loan runs for the full term. It does not account for early repayment, missed payments, a changing rate, or charges imposed under a loan agreement. For a variable-rate loan, the displayed amount is only a scenario using the APR entered as though it remained unchanged.

What Changes a Loan Payment?

  • Principal: Borrowing more increases the amount that must be repaid and generally raises the payment.
  • APR: A higher rate increases the interest charged in each period, all else equal.
  • Term: Spreading repayment across more months usually lowers the required monthly installment, but can increase total interest because the balance remains outstanding longer.
  • Payment timing and fees: A different first-payment date, financed fee, or interest convention can make a lender’s actual schedule differ from this estimate.

For the same principal and rate, extending the term does not make the borrowed amount disappear: it changes how quickly principal is repaid. Compare both the monthly figure and the total cost shown, while remembering that the calculator does not judge whether a particular payment fits a household budget.

Common Errors and Limits

One frequent mistake is mixing up APR and the periodic rate. The formula needs a monthly decimal rate, not the annual percentage entered as-is; the calculator performs the conversion by dividing APR by 1,200. Another is entering the term in months when the field requests years. For example, enter 60 months as 5 years. Check that the principal is the amount financed after any down payment or fees that are included in the loan.

This formula is designed for a fully amortizing loan with equal monthly payments and a positive APR. It does not model interest-only periods, balloon payments, irregular installments, promotional rates, rate resets, or a payment schedule with extra principal. If a loan has those features, its contract or lender-provided schedule is needed to calculate its specific payment path. The calculator also does not determine eligibility, lender fees, or the APR that may be offered; obtain those figures from the lender.

Frequently Asked Questions

How do I calculate a monthly payment with interest?
Convert annual APR to a monthly decimal by dividing it by 1,200, convert the term to months, and use the amortizing-payment formula shown above. The calculator applies that formula to the values you enter.

Does the interest rate mean APR?
This calculator’s rate field is annual APR entered as a percentage. The formula treats APR as a nominal annual rate and divides it by 12 to get the monthly rate; a lender may explain its quoted rate and APR separately.

Why is total interest higher for a longer loan term?
A longer term generally means more payment periods. Even if each payment is smaller, interest can accrue for more months before the balance is fully repaid.

Does the payment include taxes and insurance?
No. The result covers principal and interest under the stated assumptions. Taxes, insurance, PMI, escrow, and fees are not included unless they are already part of the principal you enter.

Why does my lender’s payment differ from this estimate?
The lender may use a different payment date, daily-interest method, rounding schedule, financed fees, or loan terms. Compare the calculator’s inputs with the loan disclosure and repayment schedule.

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 | $ | p * (apr / 1200) / (1 - (1 + apr / 1200) ^ -(yrs * 12)) | 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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