calculate amortisation

What does amortisation mean?

Amortisation is the process of paying off a loan through regular payments over time. Each payment typically includes two parts: interest (the cost of borrowing) and principal (the amount that reduces what you owe). At the beginning of most loans, more of your payment goes to interest. Later, more goes to principal.

If you are trying to calculate amortisation for a mortgage, car loan, or personal loan, the key idea is the same: your payment is structured so that the balance reaches zero at the end of the term.

How the amortisation calculation works

1) Monthly payment formula

For a standard fixed-rate loan, the monthly payment is calculated from:

• Principal (P) — the amount borrowed
• Monthly rate (r) — annual rate divided by 12
• Total payments (n) — years multiplied by 12

Once the payment is known, each month is calculated in sequence:

• Interest for month = current balance × monthly rate
• Principal paid = payment − interest
• New balance = old balance − principal paid

2) Why extra payments matter

Extra monthly payments reduce principal faster. Because interest is charged on the remaining balance, paying principal early usually lowers total interest and shortens the loan term.

How to use this calculator effectively

• Start with your exact loan amount and interest rate from your agreement.
• Use the real loan term (for example, 15 or 30 years).
• Try several extra-payment scenarios (e.g., $50, $100, $250) and compare savings.
• Review the amortisation table to see when your balance drops below key milestones.

The schedule shown above gives you month-by-month transparency into payment, principal, interest, and remaining balance. This can help with budgeting, refinancing decisions, and early payoff planning.

Example interpretation

Suppose your monthly payment is $1,896, and you add an extra $200 each month. The calculator may show:

• Fewer total payments
• Lower total interest paid
• An earlier payoff date

This is the core power of amortisation analysis: small consistent actions can produce large long-term savings.

Common mistakes when calculating amortisation

• Using annual interest directly instead of dividing by 12 for monthly calculations.
• Ignoring fees, taxes, or insurance (especially for home loans).
• Assuming every loan compounds the same way without checking terms.
• Forgetting to re-run calculations after rate changes or refinancing.

Final thoughts

Learning how to calculate amortisation is one of the most practical personal finance skills. It helps you move from “How much is my monthly payment?” to “What is this loan really costing me over time?” Use the calculator above to model scenarios, reduce interest, and build a smarter repayment plan.