Fixed Personal Loan Comparison Calculator

This fixed personal loan comparison calculator estimates the monthly payment and total interest for a fixed-rate personal loan from its amount, APR, and term. Enter the figures shown in a lender’s disclosure to see the payment schedule’s basic cost; the calculation does not compare lender offers or include fees.

Formula

The calculator uses the standard level-payment formula for a loan with a fixed annual percentage rate and monthly payments. It treats the APR divided by 12 as the monthly interest rate, and assumes the same payment is made at the end of each month.

• p is the amount borrowed, in dollars.
• apr is the annual percentage rate, entered as a percent (for example, 8 means 8%).
• r is the monthly rate as a decimal: apr ÷ 1,200.
• n is the number of monthly payments: years × 12.
• pmt is the monthly payment in dollars: p × r ÷ [1 − (1 + r)⁻ⁿ].
• int is estimated total interest in dollars: pmt × n − p.

The displayed payment is rounded to cents by the calculator’s display. Total interest is calculated from the payment expression and number of months, then displayed to cents. A lender’s actual payment and final instalment can differ because of its calculation conventions, payment dates, rounding, or charges.

Worked Example

Using the default inputs—$20,000 borrowed, 8% APR, and five years—the term is 5 × 12 = 60 monthly payments. The monthly rate is 8 ÷ 1,200 = 0.0066667.

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

This is an estimate under the stated assumptions. It is not a lender quote, and the figures should not be interpreted as an offer or a prediction of approval.

Assumptions

• The interest rate stays fixed for the full term.
• Payments are equal, made monthly, and occur at the end of each period.
• Interest is modelled monthly at APR ÷ 12.
• Fees, taxes, insurance, and other charges are not included.
• The calculation assumes the full entered amount is advanced and repaid through the scheduled instalments.

How to Compare Fixed Personal Loans

A fixed-rate personal loan generally means its stated interest rate does not change during the agreed term. “Fixed” does not necessarily mean every part of the borrowing cost is fixed: an origination charge, late charge, or other fee may apply, and the amount you receive could differ from the amount you repay. Compare the written offer’s APR, amount financed, payment amount, term, fees, and total repayment rather than relying on a monthly payment alone.

For a fair calculator comparison, use the same borrowing amount for each offer and enter each offer’s APR and term. A shorter term often produces a larger scheduled payment but fewer payments; a longer term spreads repayment over more months and can increase total interest. The calculator makes that trade-off visible, but it does not decide which payment or term fits a person’s circumstances.

• Check whether the quoted loan amount is the amount you will receive or the amount before a fee is deducted.
• Confirm whether the APR supplied by the lender includes charges and which charges are included.
• Compare the total of scheduled payments, not just the monthly instalment.
• Look at the repayment schedule and ask how the final payment, payment dates, and any optional services are handled.

What the Results Mean—and What They Leave Out

The monthly payment is a level-payment estimate: each scheduled payment is assumed to cover interest due for that period and reduce the outstanding principal. Early in repayment, a larger share of a payment generally goes to interest than later, because interest is calculated on the remaining balance. The total-interest figure is the estimated sum of interest across the full schedule, not the total amount repaid. Add the original loan amount to total interest to obtain the modelled amount of principal plus interest.

For example, the default calculation estimates $20,000 of principal plus $4,331.80 of interest, or $24,331.80 in scheduled principal and interest payments. It does not establish how much cash a borrower receives after any deductions. For a real offer, obtain the lender’s itemized figures; enter the disclosed APR and term rather than guessing or substituting a promotional rate.

APR and the interest rate are related but not always interchangeable descriptions. APR can reflect certain borrowing costs under the lender’s calculation, while the contractual interest rate is used to accrue interest. This calculator uses the entered APR as the rate for its monthly payment formula, a simplifying assumption. If an offer’s APR incorporates fees or is calculated differently, the result may not reproduce its payment schedule exactly.

Common Comparison Problems and Limits

Comparisons can mislead when inputs do not describe equivalent offers. A loan with a fee deducted from proceeds, for instance, may have the same stated principal as another loan but deliver less money. Similarly, an advertised payment may exclude a charge or may assume a different term. Read the disclosure for the amount financed, APR, payment count, and fees, and use consistent inputs where possible.

• Using the wrong term unit: enter years, not months. Five years is entered as 5, and the formula converts it to 60 payments.
• Confusing APR formats: enter 8 for 8%, not 0.08. The formula performs the percent conversion.
• Ignoring fees: fees are not an input here, so the results are not an all-in cost comparison.
• Assuming early payoff is modelled: the total interest assumes all scheduled payments occur. It does not estimate a payoff quote or the effect of extra payments.
• Rounding differences: actual lenders may round interest and payments at different points, leading to small differences from the estimate.

The formula is for a fixed rate and regular monthly instalments. It is not suitable for a variable-rate loan, irregular payment schedule, interest-only period, skipped payment, or a contract with a changing balance structure without additional inputs. To compare a real offer accurately, use the lender’s disclosed figures and ask for clarification about anything omitted from its payment quote.

Frequently Asked Questions

What does fixed mean on a personal loan?
A fixed rate means the stated interest rate is set rather than changing with a reference rate during the specified period. Check the agreement for the exact term and whether fees or other charges can still apply.

Does a fixed personal loan payment ever change?
The scheduled principal-and-interest payment is generally designed to stay level under a fixed-rate, regular-payment arrangement. Fees, missed payments, changed payment dates, or contract terms can affect what is actually owed; check the lender’s schedule.

Is APR the same as the interest rate?
Not necessarily. APR can incorporate certain loan costs, while the contractual interest rate is used to calculate interest. This calculator uses APR as its rate input for an estimate, so its result may not match a lender’s exact schedule.

Why can two loans with the same monthly payment have different costs?
The term, amount borrowed, fees, and APR may differ. A payment figure alone does not show how many payments are due or how much is repaid overall.

Does this calculator include origination fees or early repayment?
No. It excludes fees and assumes the scheduled payments continue through the full term. Check the lender’s disclosure for fees and request a payoff figure for an early repayment estimate.

The result is an estimate, and the lender’s disclosure gives the exact figures.

Related

• Loan Installment Schedule Calculator and Guide
• Loan Installment Formula and Monthly Payment
• Loan Installment Calculator: Estimate Monthly Payments

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