Personal Installment Loan Payment Calculator

A personal installment loan is money borrowed as a lump sum and repaid in scheduled payments over a set term. This calculator estimates the monthly payment and total interest from the amount, annual percentage rate (APR), and term you enter.

Formula

The calculator uses the standard fixed-payment amortization formula. It assumes equal monthly payments and a constant monthly rate, calculated as the annual APR divided by 12.

• p is the amount borrowed, in dollars.
• apr is the annual percentage rate, entered as a percentage, such as 8 for 8%.
• r is the monthly rate as a decimal: r = apr / 1200.
• n is the number of monthly payments: n = years × 12.
• pmt is the monthly payment, in dollars.
• int is estimated total interest over the full term, in dollars.

In symbols, the unrounded payment is pmt = p × r / [1 − (1 + r)⁻ⁿ]. The displayed payment is rounded to cents. Total interest is calculated using that displayed payment: int = pmt × n − p. Actual lender calculations may differ because of payment dates, daily interest, fees, or other contract terms.

Worked Example

Using the calculator’s defaults—$20,000 borrowed, 8% APR, and a five-year term:

1. Convert APR to a monthly decimal rate: 8 / 1200 = 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] = $405.53 per month, rounded to cents.
4. Calculate interest using the rounded payment: $405.53 × 60 − $20,000 = $4,331.80.

These are estimates under the formula’s assumptions. Rounding each payment to cents can make the final scheduled payment differ slightly from the others in a lender’s actual amortization schedule.

How a Personal Installment Loan Works

With an installment loan, a borrower receives a specified principal amount, then repays it through a series of payments. A payment generally covers interest accrued for the period and reduces some principal. Early in a fully amortizing loan, a larger share of each payment goes toward interest; as the outstanding balance falls, more goes toward principal.

“Personal loan” describes a broad category, not one universal contract. Loans may be secured by collateral or unsecured, and their uses, rates, fees, payment schedules, and eligibility terms vary. The calculator models only a fixed-rate loan with equal monthly payments. It does not establish whether a borrower qualifies or show the terms any particular lender may offer.

How to Use and Interpret the Estimate

Enter the loan principal you expect to borrow, the APR supplied in a lender’s disclosure or other reliable quote, and the term in years. The first result is the estimated monthly payment; the second is estimated interest over all scheduled payments. To understand the full cash outlay under this simplified model, add the principal to total interest.

For example, the default estimate implies 60 payments of $405.53, or $24,331.80 in payments in total. Of that amount, $20,000 repays principal and $4,331.80 is estimated interest. A longer term usually spreads repayment across more months and can lower the scheduled payment for the same principal and rate, while increasing the number of periods during which interest accrues. The exact outcome depends on the stated terms and payment calculation.

Use the actual proposed loan amount, APR, and term when available. An advertised or preliminary rate may not be the rate in a final offer. If the lender quotes an origination fee or deducts fees from the amount paid to you, the amount you receive may be less than the principal used to calculate payments.

Costs and Limits the Calculator Does Not Show

APR is intended to express borrowing cost as an annual rate, but a single calculator input cannot represent every contract detail. Check the lender’s written disclosure for the amount financed, payment amount and dates, total of payments, fees, and any conditions that affect the balance. This page does not add fees to principal or calculate a separate net amount received.

• Variable rates: A rate that can change will not follow a fixed-rate schedule, so future payments or total interest may differ.
• Irregular timing: Late, early, skipped, or extra payments can change interest and payoff timing.
• Fees and add-ons: Application, origination, late-payment, or optional product costs are not included unless reflected in the rate and contract figures you enter.
• Payment rounding: Lenders may round each payment or adjust the final payment, which can create a small difference from this estimate.

Do not treat the estimate as an approval decision or as a complete measure of a loan’s cost. To compare written offers on an arithmetic basis, use their actual payment schedules and account for fees and the amount you would receive, rather than comparing monthly payments alone.

Common Misunderstandings

A monthly payment is not the same as the total cost of borrowing. Two loans can have different terms and payments, and the smaller monthly payment does not by itself indicate which has lower total interest or fewer fees. Likewise, the calculator’s “total interest” is not the same as the total amount repaid: principal is not interest.

Another common misconception is that a personal installment loan is always unsecured or can be used for any purpose. Those details depend on the particular agreement. Read the loan documents for restrictions, collateral terms, prepayment treatment, and the exact method used to calculate interest. This calculator does not model those contract provisions.

Frequently Asked Questions

What is a personal installment loan?
A loan that provides a lump sum and is repaid through scheduled payments over an agreed period. The payment structure and other terms depend on the contract.

How do I calculate a personal loan payment?
For a fixed-rate loan with equal monthly payments, convert the APR to a monthly rate, determine the number of payments, and use the amortization formula shown above. This calculator performs those steps and rounds the payment to cents.

Does the monthly payment include fees?
Not separately. The estimate uses only the principal, APR, and term entered. Check the lender’s disclosure for fees and for whether any fee is included in the amount financed or APR.

Why can my lender’s payment differ from this result?
The lender may use different payment dates, rounding, fee treatment, or interest calculations. Variable rates and contract-specific terms can also affect the schedule.

Does a longer loan term reduce total interest?
Not necessarily. A longer term generally means more payment periods, so total interest can rise even when the scheduled monthly payment is lower. Calculate using the exact offered terms to see the estimate.

Assumptions

• The interest rate is fixed throughout the loan 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, PMI, escrow, late charges, and extra payments are not included.

This result is an estimate; the lender’s disclosure gives the exact figures.

Related

• Final Installment Loan Payment Calculator
• Fifth Third Bank Installment Loan ZIP Code Explained
• Emergency Installment Loan Calculator and Options

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