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Extra repayment calculator

What paying a little more each month does to your loan: the years it removes, the interest it saves, and how early the payoff date moves.

$
%
30 years
$

Every dollar comes straight off the balance.

Monthly repayment

$3,935.97

48% of everything you repay is interest

Total interest
$557,576
Total repaid
$1,157,576
Paid off in
24.6 years
Balance owing: $600,000Balance owing: $589,066Balance owing: $577,446Balance owing: $565,097Balance owing: $551,974Balance owing: $538,027Balance owing: $523,205Balance owing: $507,453Balance owing: $490,713Balance owing: $472,923Balance owing: $454,017Balance owing: $433,925Balance owing: $412,572Balance owing: $389,880Balance owing: $365,764Balance owing: $340,136Balance owing: $312,899Balance owing: $283,954Balance owing: $253,193Balance owing: $220,502Balance owing: $185,761Balance owing: $148,839Balance owing: $109,602Balance owing: $67,903Balance owing: $23,588
Principal and interest by year
Breakdown of Monthly repayment
Amount borrowed$600,000
Interest$557,576
Total repaid$1,157,576
  • Paying an extra 300 each period saves 151,371.41 in interest and clears the loan 5.4 years sooner.

On $600,000 at 6.1% over 30 years, an extra $300 a month clears the loan about 5 years early and saves roughly $150,000 of interest.

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Over the life of it

How this is calculated

Extra payments skip the interest entirely

A scheduled repayment covers accrued interest first. An extra payment has no interest to cover, so all of it reduces the balance — and every future interest charge is calculated on that smaller number.

interest this period = balance × periodic rate

Early payments are worth far more than late ones

An extra $300 in year 1 of a 30-year loan avoids 29 years of compounding on that amount. The same $300 in year 25 avoids five. Front-loading is why a modest extra payment removes years rather than months.

The saving compounds against the rate

At 6.1%, $300 a month on $600,000 saves around $150,000. At 4% the same payment saves closer to $80,000. The higher the rate, the more each extra dollar is worth — which is the opposite of most people’s instinct to wait for lower rates.

Worked example: $600,000 at 6.1% over 30 years with $300 extra a month
Inputs
Balance$600,000
Rate6.1%
Term30 years
Extra$300 a month
Result
Time savedabout 5 years
Interest savedabout $150,000
Cost$300 a month

That is roughly a 4-to-1 return on the extra money paid in — before any tax consideration, and with none of the market risk an investment carries.

What this assumes
  • A constant interest rate for the full term.
  • Extra payments made every period from the start.
  • No redraw or withdrawal of the extra payments.
  • No early repayment penalty.
Where this commonly goes wrong
  • Fixed-rate loans usually cap extra repayments and charge a break fee beyond the cap, so the saving shown here may not be available until the fixed period ends.
  • Some lenders hold extra payments as advance instalments rather than reducing the balance, which saves nothing — check that the payment reduces principal.
  • Clearing higher-rate debt first beats extra mortgage payments: a 20% card balance costs more than three times as much per dollar as a 6.1% mortgage.

Questions

How much does paying extra on my mortgage save?

On $600,000 at 6.1% over 30 years, an extra $300 a month saves roughly $150,000 of interest and clears the loan about 5 years early — around a 4-to-1 return on the extra money paid in.

Is it better to pay extra or invest?

Paying extra returns exactly your interest rate, with no market risk and no tax on the saving. At 6.1% that is a high bar for an investment to clear once risk and tax are counted.

Should I pay fortnightly instead of monthly?

Half the monthly amount every fortnight means 26 half-payments a year — the equivalent of 13 monthly ones. That extra payment alone typically removes four to five years from a 30-year loan without changing your budget.

When is the best time to make extra repayments?

As early as possible. An extra $300 in year 1 of a 30-year loan avoids 29 years of interest on that amount; the same $300 in year 25 avoids five. The first years carry almost all the benefit.

Can I make extra repayments on a fixed-rate loan?

Usually only up to a cap, often a few thousand dollars a year, with a break fee beyond it. Variable-rate loans generally allow unlimited extra payments, which is one of the real trade-offs when fixing.

Should I pay off my mortgage or other debt first?

Highest rate first, almost always. A credit card at 20% costs more than three times as much per dollar as a 6.1% mortgage, so extra mortgage payments while carrying card debt lose money every month.

Related tools

Sources

This calculator does arithmetic on the figures you enter. It does not account for tax, fees, or your personal circumstances.

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