Extra repayment calculator

A little extra each month attacks the principal directly — and every dollar of principal gone stops earning interest against you for decades. This shows exactly what extra repayments and lump sums save on your loan.

What extra repayments save on a $600,000 loan

On a $600,000 loan at 6.2% over 30 years ($3,674.81 a month standard):

Month-by-month simulation from the same tested engine as the calculator — not the "×12×years" shortcut.

The fortnightly trick, honestly explained

"Pay fortnightly and save thousands" is real, but only one version of it. Take your monthly repayment, halve it, and pay that every fortnight. Because the year holds 26 fortnights, you make the equivalent of 13 monthly repayments instead of 12 — one whole extra repayment a year, disguised as rounding. On the loan above that's like an extra $306 a month. If your bank instead calculates a "true" fortnightly amount (monthly × 12 ÷ 26), nothing extra happens — check which one you're getting.

Prefer keeping access to the cash? An offset account saves identical interest while the money stays spendable — the better home for an emergency fund, and the safer choice tax-wise if your home might become a rental someday.

Lump sum now, or the same money monthly?

Timing beats ritual. Put $24,000 in as a single lump today (a bonus, an inheritance, a tax refund pile) and this loan saves about $115,000 of interest and finishes 3 yrs 1 mo early. Drip the identical money in as $200 a month for ten years, then stop, and the saving is about $82,000 with 2 yrs 4 mos cut. Both are worth having, but the lump saves more interest and finishes sooner: every dollar of the lump starts avoiding interest in the first month, while the last of the drip arrives ten years later. The practical reading: never hold a windfall back to "spread it out"; the loan rewards immediacy.

One caution on where the extra dollars live. Paid straight into the loan, they're reachable only via redraw, if the loan has it — a facility on the lender’s terms, which can need its consent and limit how much and how often, and which quietly changes the tax character of the borrowing if the home later becomes a rental (redrawn money is treated as new borrowing, deductible only if redrawn for investment). If either of those bites, the offset structure gives you the same interest saving with none of the strings.