A loan payment calculator estimates the fixed monthly payment needed to repay a loan from its amount, annual percentage rate (APR), and term. Enter those three figures to see the payment and the total interest implied by the calculation.
Formula
The calculator uses the standard fixed-payment loan formula. It converts the annual APR to a monthly rate, then calculates the payment that amortizes the starting balance over the number of monthly payments.
- Monthly payment: M = P × r ÷ [1 − (1 + r)−n]
- Total interest: I = M × n − P
- Monthly rate: r = APR ÷ 1,200
- Number of payments: n = loan term in years × 12
Here, P is the loan principal in dollars, APR is the annual percentage rate entered as a percentage, r is the monthly rate as a decimal, n is the number of monthly payments, M is the monthly payment in dollars, and I is total interest in dollars. The displayed payment is rounded to cents; the total-interest result uses that displayed payment multiplied by the number of months, then subtracts principal.
Worked Example
With the default inputs, the principal is $20,000, APR is 8%, and the term is 5 years. Convert the rate and term first:
- Monthly rate: r = 8 ÷ 1,200 = 0.0066667
- Number of payments: n = 5 × 12 = 60
Substitute into the payment formula:
M = 20,000 × 0.0066667 ÷ [1 − (1.0066667)−60] ≈ $405.53 per month.
Using the calculator’s rounded monthly payment, total interest is $405.53 × 60 − $20,000 = $4,331.80. The modeled total paid is therefore $24,331.80. Actual statements can differ because lenders may use different payment dates, day-count methods, rounding, fees, or other contract terms.
Assumptions
- The interest rate is fixed for the entire term.
- Payments are equal, made monthly, and begin one month after the loan starts.
- Interest is modeled monthly at APR divided by 12.
- The calculation does not include fees, taxes, insurance, PMI, escrow, late charges, or optional add-ons.
When to Use a Payment Estimate
Use the calculator to understand the basic payment implied by a stated principal, rate, and term, or to check how those inputs affect repayment arithmetic. It can help organize questions before reviewing a lender’s payment schedule, but it does not determine eligibility, approval, or what amount a person can afford.
For example, holding the rate and term constant while increasing the principal raises the calculated payment. Holding principal and rate constant while extending the term generally lowers each scheduled payment, while increasing the number of payments over which interest accrues. These are formula relationships, not a recommendation about which loan structure to choose.
Enter the principal that is actually being financed rather than an asset’s sticker price if a down payment, trade-in, or other amount changes the loan balance. Use the APR and term stated in the estimate or disclosure. If a quoted rate is variable, changes over time are not represented by this fixed-rate calculation.
How to Read the Results
Monthly payment is the modeled amount applied each month under the assumptions above. In a fully amortizing loan, each payment covers that period’s interest and reduces principal; the portion going to principal generally changes over time. The displayed figure is not necessarily the complete monthly cost of owning a car or home, since insurance, taxes, maintenance, and other expenses may sit outside the loan payment.
Total interest estimates the interest paid across all scheduled payments in this simplified model. It is not the total amount repaid: add the original principal to total interest to get the modeled amount of principal and interest together. If fees are financed, they may increase the actual amount borrowed; if paid separately, they are not included here.
Rounding matters. The calculator rounds the monthly payment to cents and uses that rounded figure for the total-interest arithmetic. A lender may calculate interest daily or adjust the final payment to clear a small remaining balance, so a displayed estimate should not be treated as a payoff quote.
Limits and Common Mistakes
- Confusing APR with a monthly rate: Enter APR as an annual percentage, such as 8, not 0.08. The formula divides by 1,200 to obtain the monthly decimal rate.
- Mixing years and months: Enter the term in years. A five-year term means 60 monthly payments, not five payments.
- Using the wrong balance: The amount borrowed may differ from a purchase price after down payment, financed fees, or other adjustments.
- Assuming every loan is level-payment: Interest-only periods, balloon payments, changing rates, irregular schedules, and some credit arrangements do not follow this formula throughout.
- Treating the result as a statement amount: Payment dates, lender rounding, fees, and contract-specific calculation methods can change amounts due.
This tool models a conventional fixed-rate, fully amortizing loan with monthly payments. It does not calculate APR from fees, an amortization schedule, a payoff balance on a particular date, or the effect of extra payments. Those questions require additional inputs and may require the lender’s calculation method.
Frequently Asked Questions
What is a loan payment receipt? A loan payment receipt is a record or confirmation that a payment was received and credited to an account. It is different from this calculator’s estimated payment amount; obtain a receipt or transaction confirmation from the loan servicer after a payment is processed.
How do I calculate a monthly loan payment? Convert APR to a monthly decimal rate by dividing by 1,200, convert the term to monthly payments, and apply the fixed-payment formula shown above. This calculator performs those steps for the entered values.
Does the monthly payment include interest? The calculated payment includes principal and interest under the stated assumptions. It excludes separate costs such as taxes, insurance, and fees unless those costs are included in the loan principal or separately modeled.
Why does my lender’s amount differ? A lender’s figure may reflect fees, a different financed balance, payment timing, daily interest, rounding, variable rates, or other loan terms that this estimate does not model. Check the lender’s disclosure or account statement for the contract figures.
Can I use this for a variable-rate loan? It can show a hypothetical payment at one entered rate, but it cannot forecast future payments if the rate changes. Recalculate with a revised rate for a separate estimate, recognizing that this is not a projection of future terms.
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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