calculate-loan

01 Loan payments

Total Loan Cost Calculator: Payments and Interest

Calculator No. 01-6258 · Updated · Formula and assumptions shown below

Monthly payment $405.53
Total interest
$4,331.67
= Monthly payment × loan term × 12 − loan amount
Loan amount
$20,000
Input
Interest rate (APR)
8 %
Input
You enter
Loan amount ($), Interest rate (APR) (%), Loan term (years)
You get
Monthly payment ($), Total interest ($)
Rounding
2 dp

Estimate for education, not financial advice. The result follows from the numbers you enter and the formula shown. It is not a quote or an offer, and it does not include fees, taxes or insurance unless the calculator asks for them. Ask your lender for the exact figures.

This total loan cost calculator estimates the amount paid over a fixed-rate loan’s full term by combining the monthly payment and total interest. Enter the loan amount, APR, and term to see the payment and the total cost of principal plus interest.

Formula

The calculator first finds the fixed monthly payment for a fully amortizing loan, then multiplies that payment by the number of monthly payments and subtracts the amount borrowed to estimate total interest. Thus, total payments (the principal plus interest cost) equal the monthly payment times the number of months.

Let P be the loan principal in dollars, a the annual percentage rate (APR) as a percentage, r = a / 1200 the monthly rate as a decimal, and n = 12 × y the number of monthly payments for a term of y years. The monthly payment is:

M = P × r / [1 − (1 + r)−n]

Total interest is I = M × n − P. Total payments are T = M × n. All three money amounts are in dollars; displayed payment and interest are rounded to cents. The interest total uses the rounded monthly payment, as a real payment schedule is made in cents.

Worked Example

Using the calculator’s defaults: principal P = $20,000, APR a = 8%, and term y = 5 years.

  1. Convert the APR to a monthly rate: r = 8 / 1200 = 0.0066667.
  2. Find the payment count: n = 5 × 12 = 60 months.
  3. Apply the payment formula: M = 20,000 × 0.0066667 / [1 − (1.0066667)−60] ≈ $405.53 per month.
  4. Multiply the rounded payment by the number of payments: T = $405.53 × 60 = $24,331.80.
  5. Subtract the original principal: I = $24,331.80 − $20,000 = $4,331.80 in total interest.

These results describe scheduled payments under the stated assumptions. The total paid is not just the interest: it includes repayment of the original $20,000 principal as well.

What Total Loan Cost Means

“Total loan cost” can mean different things in everyday conversation. This calculator’s total interest is the borrowing cost represented by interest on the balance. Total payments add that interest to principal. Neither figure automatically includes fees or other costs associated with borrowing or owning what the loan finances.

For example, a $20,000 loan repaid through 60 payments of $405.53 has $24,331.80 in scheduled payments and $4,331.80 in interest using this calculation. If a lender also charges an origination fee, or a vehicle or home loan involves separate expenses, those costs are not reflected here. Read a lender’s written disclosures for the complete figures and their definitions.

How to Use and Read the Result

  • Loan amount: Enter the principal being borrowed, not the amount you expect to repay overall. If fees are financed into the loan, use the principal that actually accrues interest, if known.
  • APR: Enter the annual percentage rate as a percentage, such as 8 for 8%, not 0.08. Use the lender’s figure for the specific loan offer; the default is only an example.
  • Term: Enter the repayment term in years. The calculator converts it to 12 monthly payments per year.
  • Monthly payment: This is the calculated level payment that covers interest and repays principal over the selected term, assuming payments are made as scheduled.
  • Total interest: This is the estimated sum of interest paid across the scheduled payments, not the total amount paid to the lender.

To find scheduled total payments, add the displayed total interest to the loan amount. Because the payment is rounded to cents, this total follows the payment-times-months method. A lender’s actual final payment can differ slightly because of rounding, payment dates, or account-specific terms.

What the Estimate Leaves Out

The formula models a fixed APR and equal monthly payments on a standard amortizing loan. It assumes the loan is fully repaid at the end of the stated term, without missed or extra payments. It does not include lender fees, taxes, insurance, escrow, penalties, or costs tied to collateral. It also does not model a changing rate, promotional period, balloon payment, or a payment schedule other than monthly.

APR can be defined to account for certain borrowing costs in lender disclosures, but this calculator uses the entered APR as a monthly rate for the payment formula. It does not separately identify or add fees. For an exact comparison of offers, use each lender’s complete payment schedule and disclosure rather than treating this arithmetic as a full cost quotation.

Common Mistakes and Comparisons

A frequent error is confusing total interest with total cost: interest is only the amount above principal in this model. Another is entering 8% as 0.08; the input expects 8. A longer term often produces a lower scheduled monthly payment but more payments, so comparing monthly payments alone does not show the total interest. The calculator can illustrate how entered terms affect the arithmetic, but it cannot determine which arrangement fits a person’s circumstances.

Comparisons are meaningful only when the figures refer to comparable loan amounts, APR definitions, and repayment periods, and when fees and other charges are considered separately. If the loan uses variable rates, irregular payments, or a different compounding convention, this fixed-rate estimate may not match its actual schedule.

Frequently Asked Questions

Is total loan cost the same as total interest?
No. In this calculator, total interest is the cost above the principal. Total scheduled payments include both principal repayment and interest.

Does the calculator include fees?
No. It calculates scheduled principal and interest from the inputs. Check lender disclosures for fees and any other charges.

Why can a longer loan term increase total interest?
With a longer term, the balance is repaid over more monthly periods. Under a fixed positive rate, that commonly means interest accrues for longer, even when the monthly payment is lower.

Why might my lender’s payment differ?
The lender may use different timing, rounding, payment dates, fees, or loan terms. The estimate also assumes monthly payments and a fixed rate throughout.

Can I use this for a variable-rate loan?
Only as a simplified illustration using one constant APR. It cannot predict future rate changes or their effect on payments and interest.

Assumptions

  • The interest rate remains fixed for the full term.
  • Payments are equal monthly payments made on schedule.
  • Interest is modeled monthly at APR divided by 12.
  • Fees, taxes, insurance, PMI, and escrow are not included.

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

Related

Formula used
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

Each line is one input (in, sel, list) or one result (out: label, unit, formula, decimals). How the calculators work

Method: the standard loan formula for this calculation, fixed rate and monthly compounding unless stated, rounded as each result states. Not financial advice; no lender, rate or product is recommended. See formulas and assumptions, the disclaimer or report an error.

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