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Calculators · Finance and accounting tools

Loan Instalment & Interest Calculator

Calculate monthly instalments with flat or effective interest, total interest, the instalment schedule, and early payoff.

Interest method

For reference, the current BI-Rate is 5.75% (Board of Governors decision, 21 October 2026). Bank loan rates are usually above the BI-Rate and vary by product. Simulate the BI-Rate impact

Estimate based on the rules as of 1 November 2026. Calculated on your device.

How it is calculated

  • Flat: interest is charged on the original principal for the whole tenor. Instalment = principal ÷ tenor + principal × interest ÷ 12. Common for vehicle and multipurpose loans.
  • Effective (annuity): interest on the remaining principal, with the same instalment every month. Interest makes up most of the early payments; the principal share grows over time. Common for mortgages.
  • Declining: the principal is repaid in equal parts and interest is charged on the remaining principal, so the instalment falls every month.

10% flat is not the same as 10% effective: for the same principal and tenor, total flat interest is much higher. The payoff simulation shows the remaining principal; banks may charge an early repayment penalty.