calculate-loan

01 Loan payments

Monthly Payment Calculator With Interest Rate

Calculator No. 01-1660 · 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.

This monthly payment calculator estimates the fixed monthly principal-and-interest payment from a loan amount, annual interest rate (APR), and term in years. Enter those three figures to see the monthly payment and total interest, based on a level-payment loan with monthly payments.

Formula

The calculator uses the standard fixed-payment loan formula:

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

  • P is the amount borrowed, in dollars.
  • r is the monthly interest rate as a decimal: APR ÷ 1,200. For an 8% APR, r = 8 ÷ 1,200, or about 0.0066667 per month.
  • n is the number of monthly payments: loan term in years × 12.
  • Payment is the monthly principal-and-interest amount, rounded to the nearest cent.

Total interest is calculated as the rounded monthly payment multiplied by the number of payments, minus the original loan amount: Total interest = payment × n − P. Because the payment is rounded to cents before this total is calculated, the result reflects the calculator’s regular payment assumption. A real lender may adjust the final payment slightly to account for rounding or the exact payment schedule.

Worked Example

Using the calculator’s default inputs—$20,000 borrowed, 8% APR, and a five-year term—first convert the term to months: 5 × 12 = 60 payments. The monthly rate is 8 ÷ 1,200 = 0.0066667.

Substitute those values into the formula:

Payment = round[$20,000 × 0.0066667 ÷ (1 − (1 + 0.0066667)−60), 2]

The unrounded result is approximately $405.53, so the monthly payment is $405.53. Total payments using that rounded amount are $405.53 × 60 = $24,331.80. Subtracting the original $20,000 principal gives estimated total interest of $4,331.80.

Assumptions

  • The interest rate stays fixed for the full loan term.
  • Payments are equal monthly payments made at the end of each monthly period.
  • Interest compounds monthly, using APR divided by 12.
  • The estimate excludes fees, taxes, insurance, private mortgage insurance (PMI), and escrow payments.

How to Use and Read the Results

Enter the principal you expect to borrow—not necessarily the purchase price—then enter the annual APR and the term in years. The calculator returns the scheduled monthly principal-and-interest payment first, followed by total interest over the full term. The APR is entered as a percentage: enter 8 for 8%, not 0.08. The term is in years, so enter 5 for a five-year loan rather than 60.

The payment includes two parts. Interest is charged on the outstanding balance, while the rest of each payment reduces principal. At the start of a typical amortizing loan, the balance is larger, so more of the payment goes toward interest. As principal is repaid, the interest portion generally falls and the principal portion grows. The payment stays level in this calculation because the rate and scheduled payment are assumed not to change.

This result is not necessarily the full amount due each month. For a home loan, for example, taxes, insurance, mortgage insurance, or escrowed amounts may add to the bill. Other loan products may have fees or payment structures that are not represented here. Get the actual APR, amount financed, term, and payment details from the lender’s disclosure before relying on a figure.

What Changes a Monthly Payment?

  • Loan amount: A larger principal increases the payment when rate and term remain the same.
  • APR: A higher entered rate increases the interest cost and generally raises the required payment. APR is the annual rate supplied to the calculator; the calculation converts it to a monthly rate.
  • Term: Spreading repayment over more months generally lowers the scheduled monthly payment, but leaves the balance outstanding longer and can increase total interest.
  • Payment structure: Interest-only periods, variable rates, balloon payments, skipped-payment arrangements, and irregular schedules do not match this fixed-payment formula.

For instance, comparing two terms is meaningful only when the principal and rate are held constant. A lower payment on a longer term does not by itself mean that the loan costs less overall: the total-interest result helps show the trade-off under the same assumptions.

Common Errors and Formula Limits

A frequent mistake is treating APR as the monthly rate. The formula divides the annual percentage by 1,200 to convert it to a monthly decimal; dividing by 12 alone would leave the value in percentage points and produce an incorrect result. Another common error is confusing the term’s unit. This calculator accepts years and multiplies by 12, so entering months as if they were years greatly changes the calculation.

The formula also assumes that all scheduled payments are equal and that each is made on time at the end of a monthly period. It does not model a changing rate, daily interest accrual, lender-specific rounding, late charges, upfront costs, extra principal payments, or an irregular first payment. The total-interest figure is an estimate over the entire stated term; paying early or making additional principal payments changes the outcome. At very small rates or unusual contract terms, the lender’s own payment schedule may differ from this simplified estimate.

Frequently Asked Questions

How do I calculate a monthly loan payment with interest?
Convert the APR to a monthly decimal by dividing by 1,200, convert the term to months, and use the fixed-payment formula shown above. The calculator performs those steps and rounds the payment to cents.

Is the interest rate entered as a percentage or decimal?
Enter the annual APR as a percentage, such as 8 for 8%. Do not enter 0.08 for an 8% APR; the calculator divides the percentage input by 1,200.

Does the monthly payment include taxes and insurance?
No. The result covers principal and interest only. Taxes, insurance, PMI, escrow, and fees are outside this calculation unless separately included in the amount being considered.

Why can a longer loan term have more total interest?
A longer term usually means more monthly periods in which interest can accrue. Although the scheduled payment may be lower, multiplying that rounded payment by more months can produce a larger total interest estimate.

Why might a lender’s quoted payment differ?
The quote may use different loan details, payment timing, rate treatment, fees, or rounding, and it may include costs this calculator excludes. Check the lender’s itemized disclosure for the applicable figures.

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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