calculate-loan

01 Loan payments

Loan Payment Calculator: Estimate Monthly Payments

Calculator No. 01-5091 · 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 loan payment calculator estimates a fixed monthly payment and total interest from the loan amount, annual percentage rate (APR), and term. Enter those three figures to see the payment and interest estimate; the calculation assumes regular monthly payments and a fixed rate.

Formula

The calculator uses the standard level-payment formula for a fully amortizing loan with a fixed rate:

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

  • P is the starting loan principal, in dollars.
  • r is the monthly interest rate, calculated as APR ÷ 1,200. APR is entered as a percentage per year; dividing by 100 converts it to a decimal and dividing by 12 converts it to a monthly rate.
  • n is the number of monthly payments, calculated as loan term in years × 12.
  • round(…, 2) rounds the scheduled payment to the nearest cent.

Total interest is calculated as the rounded monthly payment multiplied by the number of payments, minus the original principal: Total interest = monthly payment × n − P. Because the payment is rounded to cents first, this total follows the displayed payment rather than an unrounded theoretical amount.

Worked Example

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

  1. Convert APR to a monthly rate: 8 ÷ 1,200 = 0.0066667.
  2. Find the number of payments: 5 × 12 = 60.
  3. Substitute into the payment formula: $20,000 × 0.0066667 ÷ [1 − (1.0066667)−60].
  4. The unrounded payment is about $405.53, so the monthly payment rounded to cents is $405.53.
  5. Total interest using the displayed payment is $405.53 × 60 − $20,000 = $4,331.80.

Assumptions

  • The interest rate is fixed for the full term.
  • Payments are equal, made monthly, and begin one month after the loan starts.
  • Interest is calculated monthly using APR divided by 12, expressed as a decimal.
  • The estimate excludes fees, taxes, insurance, PMI, escrow, and any other charges not entered as calculator inputs.

When to Use a Loan Payment Calculator

Use this calculation to understand the principal-and-interest payment implied by a particular amount, APR, and repayment period. It can help you compare hypothetical scenarios on the same mathematical basis—for example, seeing how changing the term affects the scheduled payment and total interest. A longer term generally spreads repayment over more months, while the formula’s total-interest result reflects how long principal remains outstanding. These are arithmetic effects, not a judgment about which loan or term is appropriate.

Enter the loan principal rather than the total price of an item unless the full price is actually being borrowed. If a down payment, trade-in, or other amount reduces the sum financed, use the resulting principal. Use the APR supplied for the specific loan as an input; do not treat the example rate as a current market rate or as an offer. Get the actual rate and loan details from the lender.

How to Read the Results

“Monthly payment” is the calculated scheduled payment toward principal and interest. It is not necessarily the full amount due each month. For instance, a mortgage payment can include escrowed taxes or insurance, and a vehicle or personal loan may have charges outside the payment modeled here. Since the calculator has no fields for those items, it cannot include them.

“Total interest” is the sum of the rounded scheduled payments minus the original principal. It is not the total amount of all possible borrowing costs: fees and other charges are excluded. The result also assumes every payment is made as scheduled, with no missed payments, late charges, extra payments, or rate changes.

Common Mistakes and Formula Limits

  • Mixing APR formats: Enter 8 for an 8% APR, not 0.08. The calculator converts the percentage internally.
  • Using the wrong term unit: The term field is in years. Entering 60 means 60 years, not 60 months; enter 5 for a five-year term.
  • Confusing payment with total cost: A monthly principal-and-interest estimate does not include excluded fees, taxes, insurance, or escrow.
  • Rounding expectations: Payments are rounded to cents. Actual lender schedules may handle the final payment or rounding slightly differently.
  • Applying it to a changing balance or rate: This formula assumes equal payments and a fixed rate. It does not model variable rates, interest-only periods, balloon payments, irregular payment dates, or revolving credit balances.

APR is used here as a nominal annual rate divided into twelve monthly periods. The calculation does not separately model how a lender discloses APR, applies fees, or accrues interest under a particular contract. For a real loan, use the lender’s disclosed payment schedule and contract details to check the exact calculation.

Frequently Asked Questions

How do I calculate a monthly loan payment?
Use the level-payment formula with the loan principal, monthly interest rate (APR ÷ 1,200), and number of monthly payments. This calculator applies that formula and rounds the payment to cents.

Does a loan payment include interest and principal?
In this fixed-rate, level-payment estimate, the scheduled payment covers both principal and interest. The division between them changes over the repayment period, but the calculator does not display a payment-by-payment amortization schedule.

Is APR the same as the monthly interest rate?
No. APR is entered as an annual percentage. This formula converts it to a monthly rate by dividing by 1,200. The calculator does not add separately entered fees or model a lender’s full APR disclosure method.

Why is my lender’s payment different?
The lender may use different loan details, payment dates, fees, rounding, or interest-accrual conventions. The calculator also excludes taxes, insurance, escrow, and other charges unless they are part of the principal entered.

Can I use this calculator for a variable-rate loan?
Only for a simplified scenario with one assumed fixed APR and equal monthly payments. It cannot predict future rate changes or calculate a changing payment 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 | $ | 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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