Calculate Monthly Instalments and Total Interest

This tool computes equal installments (amortization), the method banks use for long-term loans: you pay the same amount every month, with more of it going to interest at first and more to principal later. You get three numbers: the monthly installment, the total interest over the term and the total repayment. Enter the rate per year; it is divided by twelve for the monthly figure, so 23 percent a year is about 1.92 percent a month. With a zero rate the amount is simply split across the months. Keep in mind that this is a mathematical model: real loans can carry fees, insurance, late penalties and a different calculation method.

This tool runs entirely in your browser. No data is sent to any server.

How to use it

1. 1

   Enter the loan amount in rial or toman, either is fine as long as you stay consistent.

2. 2

   Set the annual interest rate and the repayment term in months.

3. 3

   Compare the monthly installment, total interest and total repayment, and change the term to see the difference.

Frequently asked questions

Why does a longer term mean more interest?

Because interest applies to the outstanding balance every month. A longer term lowers the installment but adds more interest-bearing months, so the total goes up.

Do I enter a monthly or an annual rate?

Annual. The tool divides by twelve itself. If you put a monthly rate here, the real cost is several times what you expect.

Why does this differ from my bank’s figures?

Banks may include fees, insurance, a down payment or a different method. This tool models standard equal installments, for comparison and planning.