Total Cost of a Loan Calculator and Formula

Total cost input means the total amount paid over a loan’s scheduled term, including the amount borrowed and the interest generated by its payments. Enter the loan amount, annual percentage rate (APR), and term to estimate total payments and total interest; the calculator assumes fixed monthly payments.

Formula

For a fixed-rate loan repaid with equal monthly payments, calculate the monthly payment first, round it to cents, and multiply by the number of monthly payments:

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

Here, P is the starting loan principal in dollars; APR is the annual percentage rate in percent; r = APR / 1200 is the monthly rate as a decimal; n is the term in years × 12, measured in months; M is the monthly payment in dollars; C is the total of scheduled payments in dollars; and I is the interest portion in dollars. The payment is rounded to the nearest cent before calculating total cost, so the displayed total reflects repeated cent-level payments.

Worked Example

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

1. Convert the APR to a monthly rate: r = 8 / 1200 = 0.0066667.
2. Convert the term to months: n = 5 × 12 = 60.
3. Calculate the payment: M = round[20,000 × 0.0066667 / (1 − (1.0066667)⁻⁶⁰), 2] = $405.53.
4. Multiply the rounded payment by the number of payments: C = $405.53 × 60 = $24,331.80 total cost.
5. Subtract the principal: I = $24,331.80 − $20,000 = $4,331.80 total interest.

The total cost is the amount paid under the modeled schedule, not just the interest charge. The principal is included in the total, which is why total cost exceeds total interest.

What Total Cost Includes

In this calculator, “total cost” has a specific, limited meaning: the sum of scheduled monthly loan payments. Those payments repay principal and interest. The calculation does not automatically include a loan origination charge, other fees, late charges, optional products, or costs billed separately. A lender may use “total cost” or similar wording differently in a disclosure, so compare the definition and included charges before treating two figures as equivalent.

For a fuller estimate of borrowing expenses, identify charges that apply to the particular loan and add them separately if they are not already financed or included in the payment. Avoid counting the same fee twice. If a fee is added to the principal, the starting balance used for the payment calculation may need to reflect that financed amount; a fee paid upfront is not part of the monthly-payment total shown here.

How to Use and Interpret the Result

• Loan amount: Enter the principal used to calculate payments. If the amount financed differs from the amount received because charges are included, use the relevant financed balance for an apples-to-apples estimate.
• APR: Enter the annual rate as a percentage, such as 8 for 8%, not 0.08. Use the figure supplied for the loan being evaluated; the example rate is only an input.
• Term: Enter the repayment period in years. The calculator converts years to months, so a five-year term means 60 payments.
• Read the outputs together: Total cost shows all modeled payments; monthly payment shows the scheduled installment; total interest isolates the amount above the starting principal.

For comparing hypothetical loan structures, hold the principal and other assumptions constant when changing one input. A longer term generally means more payment periods, and at a positive rate it can increase the sum of payments even when each monthly installment is lower. A different APR changes both the installment and the total interest. These are mathematical effects under the model, not a recommendation about which loan to choose.

Assumptions and Limitations

• The interest rate stays fixed for the full term.
• Payments are equal, made monthly, and treated as occurring at the end of each monthly period.
• Interest is modeled monthly at APR / 12; the formula does not model a lender’s daily-balance method or other compounding convention.
• The monthly payment is rounded to cents, and total cost uses that rounded payment multiplied by the full number of months.
• Fees, taxes, insurance, PMI, escrow, and any other separately billed expenses are not included.
• The model assumes every scheduled payment is made on time and in full, with no extra payments, skipped payments, rate changes, or early payoff.

Real payment schedules can differ because of payment dates, rounding rules, variable rates, fees, or a final payment adjusted to clear the remaining balance. For an exact payoff amount or contractual payment schedule, use the lender’s figures. This calculator is educational estimate arithmetic, not financial advice.

Common Mistakes

• Entering APR as a decimal: Type 8 for 8%, not 0.08; the calculator converts the percent to a monthly rate.
• Confusing interest with total cost: Interest is only the amount above principal. Total cost includes repayment of principal too.
• Ignoring fees: A payment-only estimate is not necessarily the all-in amount paid to borrow. Check which charges are included in any quoted figure.
• Assuming extra payments are modeled: They are not. Extra principal payments can change the payoff timeline and interest, so this fixed-schedule result will not represent that scenario.
• Overinterpreting cents: The answer is precise only within the stated assumptions. A lender’s schedule may differ by a small amount due to its rounding and timing methods.

Frequently Asked Questions

Does total cost of a loan include the principal?
Yes. Here it is the sum of all scheduled payments, which repay both principal and interest. Total interest is shown separately as total cost minus the original principal.

Is total cost the same as total interest?
No. Total interest is the borrowing charge calculated by the model; total cost includes that interest plus repayment of the borrowed principal. Fees and other separate expenses may also apply but are excluded here.

Why does a longer loan term change total cost?
A longer term creates more monthly payment periods. With a positive rate, interest accrues over those periods, so the sum of scheduled payments can increase even if the monthly payment decreases.

Does this calculator include fees or insurance?
No. It models principal and interest in equal monthly payments. Check the lender’s cost breakdown for fees, insurance, taxes, or other charges, and do not add a charge twice if it is already financed.

Why might my lender’s total differ?
The lender may use different payment dates, rounding, compounding, fees, a variable rate, or a final payment adjustment. The inputs may also differ from the actual loan terms. The result is an estimate; 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 tot | Total cost of loan | $ | pmt * yrs * 12 | 2
out pmt | Monthly payment | $ | round(p * (apr / 1200) / (1 - (1 + apr / 1200) ^ -(yrs * 12)), 2) | 2
out int | Total interest | $ | tot - p | 2