Total Loan Cost Calculator: Payment, Interest and Fees

This total loan cost calculator estimates the amount paid over a fixed-rate loan’s full term, including principal and interest. Enter the loan amount, annual percentage rate (APR), and term to see the rounded monthly payment and total interest; fees and other charges are not included.

Formula

The calculator first finds the fixed monthly payment for a fully amortizing loan, rounds that payment to the nearest cent, and then subtracts the amount borrowed from all scheduled payments to estimate interest.

• Monthly payment: M = round[P × r / (1 − (1 + r)⁻ⁿ), 2]
• Total interest: I = M × n − P
• Monthly rate: r = APR / 1,200
• Number of monthly payments: n = years × 12

P is the principal, or amount borrowed, in dollars. APR is the entered annual percentage rate, expressed as a percentage. r is the monthly rate as a decimal. n is the number of monthly payments, and M is the monthly payment in dollars. I is the total interest in dollars. The total of scheduled payments is M × n; it consists of the original principal plus the calculated interest.

Worked Example

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

1. Convert the APR to a monthly decimal rate: r = 8 / 1,200 = 0.0066667.
2. Convert the term to payments: n = 5 × 12 = 60.
3. Apply the payment formula: M = round[20,000 × 0.0066667 / (1 − (1.0066667)⁻⁶⁰), 2] = $405.53 per month.
4. Calculate interest using the rounded payment: I = $405.53 × 60 − $20,000 = $4,331.80.

Thus, the scheduled payments total $24,331.80: $20,000 of principal and $4,331.80 of estimated interest. The total uses the displayed, cent-rounded payment, as specified by the calculator formula.

Assumptions

• The interest rate remains fixed for the entire modeled term.
• Payments are equal monthly payments made at the end of each monthly period.
• Interest compounds monthly at the entered APR divided by 12.
• The calculation excludes lender fees, taxes, insurance, PMI, escrow, late charges, and other costs not entered as inputs.
• The scheduled payment is rounded to cents; actual contracts may handle final-payment adjustments and rounding differently.

What Total Loan Cost Includes

“Total loan cost” can mean different things depending on the context. In this calculator, it means principal plus interest across the scheduled payments. The output labeled “Total interest” is not the all-in cost of borrowing when fees or other charges apply. For the example, the principal-plus-interest total is $24,331.80, while the interest portion alone is $4,331.80.

To estimate an all-in amount, identify the charges that apply to the specific offer and add them separately, taking care not to count a charge twice. A fee paid upfront increases the cash needed at the beginning; a fee added to the balance can increase the amount on which interest accrues. The calculator does not determine which fees apply or how a lender treats them. Ask the lender for its written cost disclosures and the figures required for a complete comparison.

How to Use and Interpret the Estimate

Enter the amount financed rather than the purchase price if a down payment or trade-in reduces the loan. Use the APR supplied for the specific offer, rather than guessing from a general rate range. Enter the term in years; the formula converts it to monthly payments. The displayed payment helps describe the modeled monthly obligation, while total interest shows how much of the scheduled payments exceeds the original principal.

Changing one input at a time can show how assumptions affect the arithmetic. For example, holding principal and APR constant while extending the term usually reduces the calculated monthly payment but increases the number of payments. The overall interest result may therefore rise. This is a mathematical effect of the modeled schedule, not a recommendation about selecting a term.

For an adjustable-rate loan, a loan with irregular payments, or a loan that includes a balloon payment, a single fixed-rate amortization calculation may not represent the contract. Use the actual payment schedule or request a calculation based on the lender’s terms.

Common Calculation Errors and Limits

• Entering a monthly rate as an APR: APR here is annual and entered as a percentage, such as 8 for 8%. The formula divides by 1,200 to obtain the monthly decimal rate.
• Using the purchase price instead of the amount financed: Include only the principal actually borrowed. Separately financed charges may be part of that principal if the lender includes them in the loan.
• Forgetting the term conversion: Five years means 60 monthly payments, not five payments.
• Treating interest as every borrowing cost: The result excludes fees and other expenses unless they are included in the amount borrowed and modeled through the payment.
• Expecting an exact payoff statement: Daily interest, payment dates, rounding conventions, extra payments, and contract-specific terms can change the amount ultimately paid.

The calculation is an estimate based on level payments and a fixed rate. It does not model payment holidays, missed payments, additional principal payments, changing rates, or lender-specific rules. Those details can alter the schedule and payoff amount.

Frequently Asked Questions

Does total loan cost include the amount borrowed?
In ordinary use, “total paid” may include principal and interest, while “interest cost” refers only to the amount above principal. This calculator reports total interest; principal plus that interest is the modeled total of scheduled payments.

Are loan fees included in this calculation?
No. Fees, taxes, insurance, and similar charges are excluded. Check the lender’s disclosures for applicable charges and whether any are financed into the loan balance.

Why can a longer loan term have a higher total interest cost?
With the same principal and rate, a longer term generally spreads repayment across more monthly periods. The payment may be lower, but interest accrues over a longer schedule. This calculator illustrates that arithmetic under its fixed-rate assumptions.

What APR should I enter?
Enter the APR stated for the particular loan offer. Do not substitute a market average or an assumed rate; obtain the actual figure and confirm how the lender defines the amount financed and included charges.

Is this the exact amount I will repay?
No. It is a simplified estimate for a fixed rate and equal monthly payments. The lender’s schedule and final disclosure may reflect fees, timing, rounding, or terms that this calculator does not model.

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

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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