Fixed Term Loan Calculator: Payment and Interest

A fixed term loan calculator estimates the level monthly payment and total interest for a loan repaid over a set number of years at a fixed annual percentage rate (APR). Enter the loan amount, APR, and term to see the estimated payment and interest; the calculation assumes regular monthly payments and excludes fees and other costs.

Formula

The calculator uses the standard amortizing-loan payment formula. It converts the annual APR into a monthly rate, then calculates the fixed payment that pays interest and gradually repays principal over the full term.

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

• P is the amount borrowed, in dollars.
• APR is the annual percentage rate entered as a percent per year.
• r is the monthly rate, calculated as APR ÷ 1200.
• n is the number of monthly payments, calculated as the term in years × 12.
• M is the monthly payment, rounded to the nearest cent.
• I is the estimated total interest in dollars, using the rounded payment for every scheduled month.

The APR input is not the decimal form: enter 8 for 8%, not 0.08. Rounding the payment to cents before calculating total interest reflects the calculator’s stated convention. Actual loan schedules can differ slightly if a lender handles the final payment or daily interest differently.

Worked Example

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

1. Convert the APR to a monthly rate: r = 8 ÷ 1200 = 0.0066667.
2. Find the number of payments: n = 5 × 12 = 60.
3. Substitute into the payment formula: M = round(20,000 × 0.0066667 ÷ [1 − (1.0066667)⁻⁶⁰], 2).
4. The monthly payment is $405.53.
5. Total of scheduled payments is $405.53 × 60 = $24,331.80. Subtract the principal: $24,331.80 − $20,000 = $4,331.80 total interest.

Assumptions

• The interest rate stays fixed for the entire loan term.
• Payments are equal, made monthly, and occur at the end of each monthly period.
• Interest compounds monthly using APR ÷ 12; the APR is treated as the nominal annual rate for this calculation.
• Fees, taxes, insurance, private mortgage insurance, escrow, and other charges are not included.
• The estimate assumes the loan is fully repaid through the stated number of payments, without extra payments, missed payments, or a different final-payment adjustment.

How to Use the Result

The monthly payment is a principal-and-interest estimate, not necessarily the full amount due on a bill. A mortgage payment, for example, may also include escrowed costs; other loan products may charge fees separately. Compare the calculator’s inputs with the lender’s loan disclosure, including whether its APR incorporates particular finance charges and whether payments are monthly.

Total interest is the difference between the sum of the modeled payments and the amount borrowed. It is not the total cost of borrowing when costs outside the calculation apply. The result also does not show the balance at a particular date; it summarizes the interest over the entire assumed schedule.

Fixed Terms, Variable Rates, and Common Errors

A fixed term means the repayment period is specified, such as five years. It does not, by itself, mean the interest rate is fixed. This calculator models both a fixed term and a fixed rate. A variable-rate loan can change its payment or payoff schedule when the rate resets, so a single fixed-rate calculation cannot represent those changes.

• Entering APR incorrectly: Use 8 for 8%. The formula itself divides by 1200 to obtain a monthly rate.
• Mixing years and months: The input is years. A 60-month term is entered as 5 years, not 60.
• Using the borrowed amount instead of the financed amount: If charges are added to the balance, confirm the amount actually financed from the loan documents.
• Ignoring payment rounding: The displayed monthly amount is rounded to cents, and the total-interest estimate uses that rounded figure.
• Assuming an extra payment is included: This calculator models only the regular payment schedule. Extra principal payments can change both payoff timing and interest.

What the Calculation Cannot Show

The formula is designed for a fully amortizing loan with level monthly payments and a positive APR. It does not model variable rates, interest-only periods, deferred payments, irregular payment dates, balloon balances, late charges, or lender-specific payment allocation. At an APR of zero, the payment would simply be principal divided by the number of payments, but the calculator requires an APR of at least 0.01% because its displayed formula divides by the monthly rate.

Use the lender’s quoted principal, APR, term, payment frequency, and itemized costs for a closer comparison. If the actual agreement uses a different compounding convention or payment schedule, its figures may not match this estimate. This calculation is educational arithmetic, not financial advice.

Frequently Asked Questions

What does fixed term mean on a loan?
It means the loan is scheduled to be repaid over a specified period, such as five years. The term alone does not tell you whether the interest rate is fixed or variable.

Does a fixed term loan always have a fixed payment?
No. A level payment is typical of a fixed-rate, fully amortizing loan, but variable rates, fees, payment changes, or nonstandard repayment structures can alter the amount due.

Does the monthly payment include fees and insurance?
Not in this calculator. It estimates principal and interest only. Check the lender’s disclosure for fees and any insurance, taxes, or escrow amounts that may apply.

Why is my lender’s total interest different?
The lender may use a different payment schedule, rate convention, rounding method, financed amount, or final-payment adjustment. Fees or a changing rate can also affect the actual figures.

Can I use this calculator for a variable-rate loan?
It can provide an illustration using one APR, but it cannot project rate changes. A variable rate may change the payment, total interest, or time needed to repay.

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

Related

• TD Zero Interest Loan? Check the Costs and Terms
• Simple Interest Loan vs Compound Interest: Key Differences
• Simple vs Compound Interest Loan Calculator Explained

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