Loan Installment Calculator

Enter the principal, monthly interest rate and term; see your monthly installment amount, total interest and month-by-month payment plan.

Runs 100% in your browser — your information is never sent to a server.
This calculation includes only the principal and interest. The actual installment your bank offers may differ due to taxes such as RUSF/BITT and one-time fees such as a file charge — check your bank's official offer for the exact amount.
Monthly Installment
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Total Repayment
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Total Interest
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Payment plan
MonthInstallmentInterestPrincipalRemaining Principal

How is a loan installment calculated?

For most personal, vehicle and mortgage loans, banks use the "equal installment" (annuity) method: you pay the same amount every month for the whole term, but the interest and principal share of that amount isn't fixed. In the early months, most of your installment is interest, because the remaining principal is still high; as the term progresses the remaining principal shrinks, so the interest share gets smaller and the principal share gets bigger. The table above shows this change month by month — as the "Remaining Principal" column approaches zero, you can see how close the loan is to being paid off.

When is this useful?

You'll get the most out of this tool when comparing offers from different banks, or checking whether a loan fits your monthly budget before applying. Try the same principal with different term options: a shorter term raises the monthly installment but lowers the total interest; a longer term lightens the installment but increases the total amount paid. The remaining-principal table is also useful if you're considering an early payoff — you can see the remaining principal after a given month and compare it against the early-payoff quote your bank gives you.

Practical tips

  • Your bank usually quotes an annual interest rate; this tool asks for the monthly rate — most banks simply divide the annual rate by 12, but confirm the exact figure with your bank.
  • Extending the term lowers the monthly installment but noticeably increases the total interest; calculating two different terms and comparing the total-interest difference is usually the most revealing comparison.
  • Export the payment plan with "Download CSV" and keep it in Excel or Google Sheets so you can compare it against the actual statement your bank sends later.
  • Don't decide based on the monthly installment amount alone; putting the "Total Interest" and "Total Repayment" figures of different banks side by side, for the same principal and term, shows more clearly which offer is actually cheaper.

The principal, interest rate and term you enter are processed entirely in your browser; no value is ever sent to OpenMoon's servers or any third-party service.

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Frequently Asked Questions

With the standard formula used for equal-installment (annuity) loans: Installment = Principal × r / (1 − (1 + r)−n), where r is the monthly interest rate (decimal) and n is the number of months. Each month the interest portion of the installment decreases and the principal portion increases; the total installment amount stays constant.

For personal loans, taxes such as the Resource Utilization Support Fund (KKDF, 15%) and Banking and Insurance Transactions Tax (BSMV, 15%, on interest) increase the effective cost; one-time fees such as file/appraisal charges and life insurance can also increase the total payment. This tool only calculates the "bare" installment based on principal + interest — ask your bank for the annual cost rate to compare offers.

When the interest rate is 0, the calculation reduces to simple division: installment = principal / term. This is useful for modeling interest-free installment campaigns (e.g. some store or credit-card installment plans).

The interest you pay each month is calculated on that month's remaining principal. The longer the term, the more slowly the principal shrinks, so you end up paying interest for more months — even though the monthly installment is lower, you pay more interest in total.

No. This is only an informational calculation tool; it isn't affiliated with any bank and doesn't submit a loan application or approval. For an actual application, you need to contact your bank.

After calculating, use the "Download CSV" button to save the month-by-month payment plan as a spreadsheet file that you can open in Excel or Google Sheets.

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