Loan Instalment Calculator

Annuity charges interest on a balance that shrinks every month; flat charges it on the original principal for the whole tenor. At the same percentage, flat costs far more. Example: Rp50,000,000 over 3 years at 12% — annuity totals roughly Rp9.8 million in interest, flat totals Rp18 million. So a 12% flat rate is not comparable to 12% annuity. This calculator shows an 'equivalent annuity rate' when you pick flat, so the comparison is fair.

For annuity: instalment = P × i × (1+i)^n / ((1+i)^n − 1), where P is the principal, i is the monthly rate (annual rate ÷ 12 ÷ 100), and n is the number of months. Flat is far simpler: instalment = (P/n) + (P × annual rate × years / n). This calculator does both, with the full schedule.

That's how annuity works, not a bank error. Because interest is charged on the outstanding balance, it's largest in month one when the debt is untouched. As principal falls, the interest share shrinks and the principal share grows. The consequence: paying off mid-tenor saves less than people expect — you've already paid most of the interest up front. The schedule shows the shift directly.

It'll be close, but usually not exact. This calculator computes pure principal and interest assuming a fixed rate throughout. Real bank figures typically add provision fees, administration, life insurance, and other product-specific charges. Some loans also use floating rates that move with the market. Use this to compare offers and plan a budget, then confirm the final number with the bank.

A common guide is that total instalments stay under 30% of monthly income, and banks commonly decline once you pass roughly 40%. Note that limit applies to ALL your instalments combined, not one loan — credit cards, vehicle finance, and paylater all count. The closer you sit to the ceiling, the less room you have when something unexpected hits.