calculate-loan

01 Loan payments

Loan Payment Calculator: Estimate Monthly Payments

Calculator No. 01-4931 · 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.

A loan payment calculator estimates a fixed monthly payment from the amount borrowed, annual percentage rate (APR), and loan term. Enter those three figures to see the monthly payment and the total interest estimated over the full term.

Formula

The calculator uses the standard fixed-payment amortization formula. It assumes the same payment is made once a month and that interest accrues at a constant monthly rate.

  • Monthly payment: M = round[P × r ÷ (1 − (1 + r)−n), 2]
  • Total interest: I = M × n − P
  • Monthly rate: r = APR ÷ 1200
  • Number of payments: n = loan term in years × 12

P is the loan principal in dollars, APR is the annual percentage rate entered as a percentage, M is the monthly payment in dollars, and I is estimated interest in dollars. For example, an APR input of 8 means 8% per year; dividing by 1200 converts it to a monthly decimal rate. The payment is rounded to the nearest cent before total interest is calculated.

Worked Example

Using the default inputs—$20,000 principal, 8% APR, and a five-year term—the number of monthly payments is 5 × 12 = 60. The monthly rate is 8 ÷ 1200 = 0.0066667.

  1. Calculate the payment factor: (1 + 0.0066667)−60 ≈ 0.6712.
  2. Substitute into the payment formula: $20,000 × 0.0066667 ÷ (1 − 0.6712) ≈ $405.53 per month after rounding.
  3. Calculate total paid using the rounded payment: $405.53 × 60 = $24,331.80.
  4. Subtract the original principal: $24,331.80 − $20,000 = $4,331.80 estimated total interest.

Assumptions

  • The interest rate stays fixed for the full term.
  • Payments are equal, made monthly, and paid at the end of each monthly period.
  • Interest compounds monthly at APR divided by 12.
  • Fees, taxes, insurance, PMI, escrow, and other charges are not included.

When to Use a Loan Payment Calculator

Use this estimate when you want to understand how principal, APR, and repayment length relate to a level monthly payment. It can help you compare hypothetical loan structures using figures you supply, or check the arithmetic behind a quoted principal-and-interest payment. The result is not an approval decision, a rate offer, or a complete monthly housing or borrowing cost.

For a meaningful estimate, use the principal that would actually be financed, rather than the purchase price if a down payment or trade-in reduces the amount borrowed. Use the APR supplied for the particular loan, and confirm whether it represents the rate and charges in the lender’s calculation. The calculator cannot look up rates or fees; obtain the relevant figures directly from the lender.

How to Read the Results

Monthly payment is the calculated regular principal-and-interest installment under the formula’s assumptions. Total interest is the sum of those rounded installments minus the original principal. It is an estimate across the entire stated term, not the interest due in one month. In the example, the payment total is $24,331.80, of which $20,000 repays principal and $4,331.80 is estimated interest.

Early in a standard amortizing loan, a larger share of each payment generally goes toward interest because the outstanding balance is larger. As principal is repaid, the interest portion declines and more of a level payment reduces the balance. The calculator reports the scheduled full-term estimate; it does not model a changing balance from extra payments, missed payments, or early payoff.

Common Mistakes and Calculator Limits

  • Entering APR as a decimal: Type 8 for 8%, not 0.08. The formula performs the percentage conversion.
  • Mixing up years and months: The term field is in years, and the formula multiplies it by 12. A five-year term means 60 monthly payments.
  • Using the wrong principal: Enter the amount financed, not necessarily the asset’s full price.
  • Expecting a complete bill: A mortgage payment may also involve taxes, insurance, escrow, or PMI; other borrowing may have charges not represented here.
  • Ignoring payment rounding: The displayed monthly payment is rounded to cents, and the total-interest calculation uses that rounded amount. A lender’s final schedule can differ because of its exact payment dates and rounding practices.

This standard formula is for a fixed-rate loan with regular level monthly payments. It does not directly model variable rates, irregular payment schedules, fees added to the balance, interest-only periods, balloon payments, or payment holidays. A 0% rate also requires a separate simple calculation because the formula divides by the monthly rate; this calculator requires a positive APR.

Frequently Asked Questions

How do I calculate a monthly loan payment?
Convert APR to a monthly decimal by dividing it by 1200, convert the term to months, then use the fixed-payment formula shown above. The calculator performs those steps and rounds the payment to cents.

Does the monthly payment include interest?
Yes. For a standard amortizing loan, each scheduled payment includes interest and principal repayment. The proportions change over time, even when the total payment stays level.

Is APR the same as the interest rate?
Not necessarily. APR is an annual percentage figure that can reflect certain borrowing costs as defined for the loan. The calculator treats the entered APR as a nominal annual rate divided by 12; check the lender’s disclosure to understand how its quoted APR and payment are calculated.

Why does my lender’s payment differ?
The lender may use a different financed amount, payment date, rounding convention, rate, or loan structure. Fees, insurance, taxes, escrow, and other charges may also affect the amount due without being included in this estimate.

Can I use this for a variable-rate loan?
Only as a snapshot under a hypothetical fixed rate. If the rate changes, the payment or repayment schedule may change too, and this calculator does not forecast those changes.

The 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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