How Extra Mortgage Repayments Save You Years and Thousands

Interest is charged on what you still owe

A mortgage is a reducing-balance loan: each period, the lender charges interest on your current outstanding balance, not on the original amount you borrowed. Your regular repayment is split between that period's interest and whatever is left over, which reduces the balance ready for the next period's calculation.

Early in a 30-year loan, most of each repayment goes to interest, because the balance — and therefore the interest charge — is still close to the full loan amount. Only late in the loan, once the balance has shrunk, does most of the repayment start going to principal. This is why the first years of a mortgage feel like they barely move the balance.

Why extra repayments punch above their weight

Every extra dollar you pay goes straight to principal, bypassing the interest-first split entirely. That shrinks the balance immediately — and because next period's interest is calculated on that smaller balance, you avoid paying interest on interest for every remaining period of the loan. A single extra payment early in a 30-year loan avoids decades of interest charges on that amount; the same extra payment made in year 25 only avoids a few years of it.

This is the core reason a modest, regular extra repayment usually beats an occasional large one of the same total size: money paid earlier has more remaining loan term left to save interest on. See it directly with the Mortgage Calculator — enter your own numbers and watch the payoff date move as you add an extra repayment.

Time saved is not proportional to money paid

Because of compounding, the relationship between extra repayments and time saved is not a straight line. The first extra dollars you add typically buy you more time-per-dollar than later ones, because they're removing balance — and its future interest — earliest in the loan's life. This is also why paying off a mortgage a few years early is realistic on a fairly modest regular extra repayment, not just for people who can throw large lump sums at it.

Extra repayments vs. investing the difference

A common question is whether it's better to pay extra off the mortgage or invest the same amount instead. The honest, simplified comparison is a straight rate comparison: paying down the mortgage guarantees a return equal to your mortgage interest rate (since that's the interest you avoid), while investing returns are variable and not guaranteed. Neither answer is universally right — it depends on your mortgage rate, your risk tolerance, whether your loan has an offset feature, and your other financial goals — but the mortgage side of that comparison is the guaranteed, risk-free one.

Before you start paying extra, check two things

• Redraw or offset availability. Confirm you can access extra repayments later if you need them, or that you're comfortable with the money being locked in.
• Early repayment fees or caps. Some fixed-rate loans limit how much extra you can pay per year without a penalty — check your loan's terms before committing to a number.

See your own numbers

The maths above is the same regardless of your currency or loan size — what changes is the scale. Plug in your own remaining balance, rate and term into the Mortgage Calculator to find your personal Mortgage Freedom Day, and see exactly how much a small regular extra repayment is worth to you in both time and interest.