Loan amortisation calculator

What an amortisation schedule shows

An amortisation schedule is the period by period breakdown of a loan, from the first repayment through to the last. Every line shows four things. What you pay, how much of that payment covers interest, how much of it reduces the amount you still owe, and the balance left once the payment lands. Add the interest column up and you have the real cost of borrowing across the full term.

Most repayment calculators stop at a single figure. The schedule is more useful because it shows the shape of the loan. Early on the balance is at its highest, so the interest charged in each period is at its highest too, and only a small slice of your payment reduces the principal. As the balance falls, the interest portion shrinks and the principal portion grows. That is why the final year of a loan clears far more debt than the first year does for exactly the same money.

How the calculation works

This calculator uses the standard annuity formula, the same arithmetic a lender applies to a fixed rate term loan. The annual rate you enter is divided by the number of repayments in a year to give a periodic rate, so 12 for monthly, 26 for fortnightly and 52 for weekly. The number of repayments is the term in years multiplied by that same figure.

In each period, interest is charged on the balance outstanding at the start of the period. Whatever remains of your repayment once that interest is met comes off the principal. The repayment amount is set so this process retires the balance precisely at the end of the term. Because every line is rounded to the nearest cent, the final repayment is adjusted by a few cents so the closing balance finishes at exactly zero rather than a little either side.

The rate is yours to enter. We do not suggest one, because the rate a lender offers depends on the product, the security, the term, the loan amount and your own circumstances. Entering a figure you have actually been quoted, or the rate on a loan you already hold, gives you a schedule that means something.

How repayment frequency changes the total interest

Switching between monthly, fortnightly and weekly repayments changes the total interest, and the reason is worth understanding. Interest accrues on the balance you are carrying, so paying more often means the balance comes down sooner and less interest builds up between payments. Across a long term the difference is real, though usually modest when the periodic amount is simply the monthly figure converted across the year.

The larger saving comes from a different habit. Some borrowers set a fortnightly repayment at half the monthly amount, which produces 26 half payments a year, the equivalent of 13 monthly repayments rather than 12. That extra repayment each year shortens the term and cuts total interest noticeably. This calculator does not assume that structure. It amortises the amount you enter across the term you set, so the comparison between frequencies here is like for like.

Before you commit to a frequency, check the loan contract. Some lenders align repayments to your pay cycle on request, others limit how often the schedule can change or apply a fee to change it, and a few calculate interest monthly regardless of how often the payments arrive.

Using the schedule when you compare loans

A schedule makes a good comparison tool. Run one scenario, note the total interest, then change a single input and run it again. Adjusting the term while holding everything else steady shows exactly what a longer term costs you in interest in exchange for the lower repayment it buys. Adjusting the amount shows how much of your borrowing capacity is going to interest rather than to the asset itself.

It also helps with payout and refinance decisions. If you are weighing up paying a loan out early, find the period you have reached and read the remaining balance alongside the interest still to come. The earlier you are in the term, the larger the share of the remaining cost that is interest, and the more there is to save by acting.

The figures here are estimates built from the inputs you supply. They exclude establishment fees, ongoing account fees, government charges and insurance, all of which affect what a loan really costs. When you want numbers that reflect an actual lender and an actual product, a broker comparison across the panel shows you the rate and the structure you would genuinely be offered.