calculate-loan

01 Loan payments

Personal Bank Loan Calculator: Monthly Payment and Interest

Calculator No. 01-8390 · 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 personal bank loan calculator estimates your monthly payment and total interest from the amount borrowed, annual percentage rate (APR), and repayment term. Enter those three figures to see the scheduled payment and the estimated interest over the full term; use the rate and terms shown in a lender’s disclosure for a closer estimate.

Formula

This calculator assumes a fixed rate and equal monthly payments. It converts the annual APR to a monthly rate, calculates the payment needed to amortize the balance over the chosen term, rounds that payment to cents, and estimates total interest using the rounded payment.

  • Monthly payment: M = P × r ÷ [1 − (1 + r)−n]
  • Total interest: I = M × n − P
  • Monthly rate: r = APR ÷ 1,200

P is the loan principal in dollars; APR is the annual percentage rate entered as a percentage; r is the monthly rate as a decimal; n is the term in months, calculated as years × 12; M is the monthly payment in dollars; and I is estimated total interest in dollars. For example, an APR of 8% gives r = 8 ÷ 1,200, not 0.08 ÷ 12.

The calculator’s displayed payment is rounded to the nearest cent. Its interest estimate multiplies that rounded payment by the number of scheduled months and subtracts the original principal. A lender may adjust the final installment by a few cents to clear the remaining balance, so the total is an estimate rather than a statement balance.

Worked Example

Using the default inputs—$20,000 principal, 8% APR, and a five-year term—the number of payments is 5 × 12 = 60 months, and the monthly rate is 8 ÷ 1,200 = 0.0066667.

  1. Payment = 20,000 × 0.0066667 ÷ [1 − (1 + 0.0066667)−60].
  2. The unrounded monthly result is about $405.53; rounded to cents, the estimated payment is $405.53 per month.
  3. Estimated total paid = $405.53 × 60 = $24,331.80.
  4. Estimated total interest = $24,331.80 − $20,000 = $4,331.80.

Assumptions

  • The interest rate is fixed for the full term.
  • Payments are equal, made monthly, and treated as occurring at the end of each monthly period.
  • Interest compounds monthly at APR ÷ 12.
  • Fees, taxes, insurance, optional products, and other charges are not included. The calculator does not model a lender’s payment schedule, fee financing, or a different final payment.

When to Use a Personal Loan Calculator

Use the estimate to understand how the amount, rate, and term affect the scheduled payment and modeled interest. It can help you compare hypothetical combinations on the same basis, but it cannot establish whether a lender will approve an application or what terms a lender will offer.

  • Enter the amount you expect to borrow, rather than an amount that also includes charges unless those charges will be financed.
  • Use the APR and repayment term from the lender’s written offer or disclosure when available. If you are exploring a scenario, label the rate as an assumption.
  • Compare the same loan amount and term when examining rate scenarios; changing several inputs at once makes the source of a payment difference harder to see.
  • Check whether the quoted payment includes any fee or optional product. This calculator treats the principal as the amount borrowed and does not add separate charges.

A personal loan is often described as an installment loan because repayment is scheduled in regular payments over a set term. The calculator represents that basic structure; actual contracts and payment schedules can contain details the formula does not capture.

How the Results Change

For the same principal and APR, a longer term generally lowers the calculated monthly payment because repayment is spread over more months, but the model also accumulates interest for longer. A shorter term generally raises the monthly payment while reducing the number of interest-charging periods. This is a mathematical relationship, not a judgment about which term fits a particular person.

At a fixed term and principal, a higher APR raises the calculated payment and interest. At a fixed APR and term, borrowing a larger principal raises both in proportion. The formula assumes the APR remains unchanged; it does not forecast future rates or account for a rate that changes during repayment.

Common Calculator Limits and Mistakes

  • Confusing APR with a monthly rate: Enter APR as a yearly percentage, such as 8, not 0.08 or 0.0067. The calculator performs the conversion.
  • Mixing years and months: The term field is in years. Five years means 60 monthly payments, not five payments.
  • Treating interest as every borrowing cost: The interest output excludes fees and other charges. A lender’s disclosure is needed to see the contractual figures and any additional costs.
  • Assuming the estimate is an offer: The calculator does not include lender-specific underwriting, approval decisions, or offer conditions. Use figures supplied by the lender for an actual loan scenario.

Rounding matters when the result is multiplied over many months. This calculator uses the rounded monthly payment to estimate total interest, while a lender may calculate interest using its own accrual and posting conventions and may adjust the final payment. Small differences do not necessarily indicate an error.

Frequently Asked Questions

What does a personal bank loan calculator calculate?
It estimates the monthly payment and total interest for a fixed-rate loan with equal monthly payments, based on the entered principal, APR, and term.

Is APR the same as the interest rate?
APR is an annual percentage figure used here as the rate input. The calculator does not break out any fees that might affect a lender’s disclosed APR; enter the figure provided for the scenario you want to estimate.

Why is the lender’s payment different from the calculator?
The lender may include fees, use different payment dates or interest-accrual conventions, or adjust the final installment. Check the lender’s disclosure for the exact schedule and charges.

Does a longer loan term mean less interest?
Not necessarily. In this fixed-rate model, a longer term usually reduces the monthly payment but increases the number of months over which interest is paid, raising modeled total interest when the principal and APR stay the same.

Does this calculator tell me whether I will be approved?
No. It performs payment arithmetic only and does not assess applications, eligibility, or lender decisions.

This result is an estimate; 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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