Personal Loan Calculator: Payments, Interest and Costs

A personal loan calculator estimates the monthly payment and total interest on a fixed-rate loan from the amount borrowed, annual percentage rate (APR), and repayment term. Enter your loan details to see an estimate; the calculation assumes equal monthly payments and does not include fees or other charges.

Formula

The calculator uses the standard fixed-payment loan formula. It converts the annual APR to a monthly rate, calculates the payment needed to repay the principal and interest over the selected number of months, rounds that payment to cents, then subtracts the amount borrowed from the sum of scheduled payments to estimate total interest.

Monthly payment: M = round[P × r ÷ (1 − (1 + r)⁻ⁿ), 2]. Total interest: I = M × n − P.

• P is the loan principal, in dollars.
• APR is the annual percentage rate entered as a percentage.
• r is the monthly rate, calculated as APR ÷ 1,200.
• n is the number of monthly payments, calculated as years × 12.
• M is the monthly payment, in dollars, rounded to the nearest cent.
• I is estimated total interest, in dollars.

APR is divided by 1,200 because a percentage must first be divided by 100 to become a decimal, then divided by 12 to express it monthly. This calculation treats the entered APR as the rate used for monthly interest; it does not separately model origination charges or other fees that might affect a lender’s disclosed APR or the amount received.

Worked Example

Using the calculator’s default inputs—$20,000 principal, 8% APR, and a five-year term—the number of payments is 5 × 12 = 60. The monthly rate is 8 ÷ 1,200 = 0.0066667, or about 0.66667% per month.

1. Substitute the values into the payment formula: M = round[20,000 × 0.0066667 ÷ (1 − (1.0066667)⁻⁶⁰), 2].
2. The unrounded payment is approximately $405.53, so the monthly payment shown is $405.53.
3. Total scheduled payments are $405.53 × 60 = $24,331.80.
4. Estimated interest is $24,331.80 − $20,000 = $4,331.80.

Both results are estimates based on the formula and rounded payment. A lender’s schedule can differ because of payment dates, rounding conventions, fees, or terms not represented here.

Assumptions

• The APR is fixed for the full repayment term.
• Payments are equal, made monthly, and are assumed to occur at the end of each monthly period.
• Interest accrues monthly at APR ÷ 12, with the APR entered as a percentage.
• The calculation excludes fees, taxes, insurance, PMI, escrow, late charges, and any optional products; none of these is an input.

How Personal Loans Work

A personal loan is generally a lump sum that a borrower repays in installments under a loan agreement. Many personal loans are unsecured, meaning they are not tied to a specific asset as collateral, but loan structures and conditions vary. The agreement sets details such as the amount advanced, interest rate, payment schedule, fees, and consequences of missed payments. Review the lender’s written disclosures for the terms that apply to a particular offer.

With a typical amortizing fixed-rate loan, each scheduled payment covers interest accrued since the prior payment and reduces principal. Early in the schedule, a larger share of the payment usually goes toward interest because the outstanding balance is higher. As the balance falls, the interest portion generally falls and more of each level payment reduces principal. The exact allocation depends on the contract and payment timing.

For example, the default estimate totals $24,331.80 in payments on a $20,000 loan, including $4,331.80 of modeled interest. That is not the same as receiving $20,000 in usable funds if an upfront fee is deducted, nor does it establish the total cost of a specific offer. Compare the amount deposited, amount owed, payment schedule, APR, and all disclosed charges as separate figures.

Costs and Choosing What to Compare

The payment amount is only one part of the cost. A longer term often lowers the required monthly payment under the same modeled rate and principal, but it also means more payment periods and can increase total interest. A shorter term can have the opposite effect. The calculator makes this trade-off visible only for the assumptions entered; actual offers can have different rates, fees, and repayment conditions.

When reviewing an offer, check the following details in its disclosure and agreement:

• Whether the quoted APR is fixed or can change, and how it is applied.
• The amount financed, the amount you would actually receive, and any fee deducted or added.
• The payment amount, first due date, number of payments, and final payment amount.
• Whether there are charges for late or missed payments, and what happens if a payment is not made.
• Whether the agreement describes any charge or restriction for paying early.

Do not treat an estimated payment as an approval decision or as a determination of affordability. A calculator cannot see a borrower’s full finances or the lender’s underwriting assessment. Use the actual figures supplied by the lender to understand a specific transaction.

Limits, Common Misconceptions and Alternatives

A common misconception is that a monthly payment alone tells you which loan costs less. It does not: a smaller payment may result from spreading repayment across more months, and fees may not be reflected in this calculator. Likewise, “total interest” here is not the same as every possible borrowing cost. It is principal repayment arithmetic under a fixed-rate, level-payment assumption.

The model also does not calculate a changing-rate loan, irregular payments, skipped or deferred payments, extra principal payments, a payoff balance on a particular date, or a lender’s exact day-by-day interest. It assumes the term produces a whole number of monthly payments. If payments are made early or late, the balance and interest allocation may differ from the estimate. For a customized payoff schedule, use the contract’s rules and payment history.

Depending on the purpose and circumstances, people may also investigate alternatives such as using savings, negotiating a payment arrangement with a provider, or comparing another form of financing. These options have different costs, risks, and eligibility requirements, which this calculator does not evaluate. It is a general arithmetic tool, not a recommendation to borrow or to select a particular option.

Frequently Asked Questions

How is a personal loan monthly payment calculated?
The payment formula uses the amount borrowed, monthly interest rate, and number of monthly payments. It calculates the level payment that amortizes the balance over the term, assuming a fixed rate and regular monthly payments.

Does a personal loan calculator include fees?
No. This calculator includes modeled principal and interest only. Check the lender’s disclosure for any origination or other fees, whether a charge is deducted from the proceeds, and the total repayment figures for the offer.

Does a longer personal loan term reduce total cost?
Not necessarily. With the same principal and rate, a longer term generally spreads repayment across more months and may lower the monthly payment, while increasing the number of periods over which interest is charged.

Is APR the same as the monthly interest rate?
No. APR is entered as a yearly percentage. This calculator converts it to a monthly rate by dividing by 1,200. An offer’s APR may also reflect details not represented by this simplified calculation.

Can I use this calculator for a variable-rate loan?
It can show an estimate for one assumed rate, but it cannot model future rate changes. If a rate varies, actual payments or total interest may differ from the fixed-rate estimate.

Why might the lender’s payment differ from this result?
Possible reasons include fees, a different rate or term, payment timing, rounding methods, a first period that is not a full month, or contract provisions not included here. The result is an estimate; the lender’s disclosure gives the exact figures.

Related

• Closing Costs vs. Down Payment: What’s the Difference?
• Is Closing Cost Included in Down Payment?
• Personal Loan Payment Calculator and Loan Features

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