Why does one extra instalment a year save so much?

Because the extra payment goes entirely to principal. A normal instalment is mostly interest early on, but an extra payment has no interest to cover, so all of it reduces the balance — and principal removed early avoids interest for the whole remaining term. On a typical 30-year loan this clears it around six years sooner.

How can fortnightly payments help if I pay the same amount?

You do not pay the same amount. Paying half the instalment every two weeks means 26 half-payments a year, which equals 13 monthly instalments instead of 12. The higher frequency helps slightly too because the balance drops sooner within each month, but the extra instalment accounts for most of the saving.

Is weekly better than fortnightly?

Only marginally. Both add up to 13 monthly instalments a year and finish at almost the same time. Weekly payments reduce the balance slightly sooner within each month, but the difference is usually a fraction of a percent. Choose whichever matches your pay cycle.

Does prepaying reduce my instalment or my tenure?

This calculator assumes prepayments reduce the tenure, which saves the most interest and is the usual default. Some lenders instead recalculate a lower instalment over the original term, which helps cash flow but saves far less. Confirm which treatment your lender applies.

Is rounding up my payment really worth it?

It is the smallest strategy here but the easiest to sustain. Rounding an instalment of 1,995 up to 2,000 costs five units a month and still shaves a couple of months off a 30-year loan. Larger increments behave like a substantial recurring extra payment.

Should I prepay the loan or invest the money instead?

Prepaying earns a guaranteed, tax-free return equal to your loan rate, while investing may earn more but with uncertainty and tax. Compare your after-tax loan rate against your expected after-tax return, adjusted for risk. High-rate debt is almost always worth clearing first.

What about prepayment penalties?

The calculator assumes there are none, which is common for floating-rate loans but not universal. Fixed-rate and some business loans can charge one to three percent of the amount prepaid. Subtract any such charge from the interest saved figure to get your true benefit.

Can I combine several strategies?

Yes. You can pay fortnightly, round each payment up, add a recurring extra and drop in an annual bonus at the same time, and the simulation applies them together. The ranked table shows each strategy on its own so you can see which single change does the most.

LoansFlagshipUpdated July 31, 2026

Extra EMI Impact Calculator

Test every way of paying your loan off early — extra instalments, rounded-up payments, lump sums, one-time prepayments, or switching to weekly or fortnightly — and see exactly how much interest and time each one saves.

How to use this calculator

Step 1
Describe the loan
Enter the amount, rate and remaining tenure of the loan you want to attack.
Step 2
Pick an acceleration strategy
Combine extra instalments, round-ups, recurring extras and lump sums however you like.
Step 3
Compare the two payoffs
Watch the animated race, then check the ranked table to see which single change wins.

Quick facts

Strategies modelled: 9, combinable
Payment frequencies: Weekly, fortnightly, monthly
Interest basis: Reducing balance
Prepayment penalty: Assumed zero

The loan

The debt you want to pay down faster.

Currency

Outstanding amount

Adjust amount

$10k$2000k

Interest rate

Adjust rate

0%20%

Remaining tenure

yrs

Adjust tenure

1 yr40 yr

Acceleration strategy

Active

Stack as many of these as you like — they are simulated together.

Payment frequency

The contractual schedule: one instalment a month.

Instalments per year

1 extra instalment a year, spread evenly.

Round every payment up

Extra payments

Extra per month

Added to every instalment.

Annual lump sum

A bonus or tax refund you can commit every year.

In month

One-time prepayment

A single payment, such as a windfall or maturing deposit.

At month

Extra payments are assumed to shorten the term rather than reduce the instalment.

Payoff comparison

6 years earlier

72 of 360 months cut

Original payoff30 yrs (360 mo)

New payoff24 yrs (288 mo)

Interest saved

$98,545

23.5%less interest

Standard plan interest: $418,527
Your plan interest: $319,982

Time saved

6 yrs

Months saved: 72
Years saved: 6
Remaining months: 0

Average monthly outlay

$2,153

$157 a month more than the standard plan.

Total repaid

$619,982

Down from $718,527 on the standard plan.

Balance comparison

Both plans start at the same balance. The gap between the curves is debt you no longer owe.

Your plan clears the balance in month 288, 6 yrs before the standard plan.

Interest paid over time

Cumulative interest under each plan. The accelerated line flattens once the loan clears.

The final gap between the two lines is $98,545 of interest you never pay.

Watch the two plans race

Play the loan forward month by month and watch your plan pull ahead.

Month 0 of 360 · 0 mo in

Standard planBalance $300,000|Interest $0

Your planBalance $300,000|Interest $0

Scrub the timeline

Every strategy, ranked for this loan

Each row is simulated separately against your loan. Apply one to load it into the calculator above.

Strategy	Payoff	Time saved	Interest saved	Outlay / month
15 instalments a yearBest saving Three extra instalments, four months apart.	17 yrs 5 mo	12 yrs 7 mo	$198,275	$2,489
14 instalments a year Two extra instalments, six months apart.	20 yrs 1 mo	9 yrs 11 mo	$158,543	$2,324
Extra 10% each month A steady top-up of a tenth of the instalment.	22 yrs 11 mo	7 yrs 1 mo	$116,640	$2,189
Weekly payments A quarter of an instalment every week.	23 yrs 9 mo	6 yrs 3 mo	$103,801	$2,162
Fortnightly payments Half an instalment every two weeks.	23 yrs 9 mo	6 yrs 3 mo	$103,388	$2,160
Annual lump sum One instalment's worth every twelve months.	24 yrs	6 yrs	$98,548	$2,153
13 instalments a year One extra instalment every year.	24 yrs	6 yrs	$98,545	$2,153
One-time prepayment 5% of the principal paid in month 12.	25 yrs 11 mo	4 yrs 1 mo	$83,332	$2,042
Round up to 100 Round every instalment up to a neat figure.	29 yrs 10 mo	2 mo	$3,496	$1,997

Outlay per month is the average of everything paid, spread across the shortened term — it is what accelerating actually costs your monthly budget. The CSV export contains the full payment-by-payment schedule for the strategy currently applied above, including the extra paid at each step.

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How early payoff is calculated

There is no closed-form formula for this. Every extra payment changes the balance that all later interest is charged on, so the payoff date has to be found by simulating the loan period by period until the balance reaches zero.

Balanceₖ = Balanceₖ₋₁ × (1 + r) − (Payment + Extraₖ)

Balanceₖ

Balance after payment k

The simulation stops at the first k where this hits zero.

Rate per payment period

The annual rate divided by the payments per year: 12 monthly, 26 fortnightly, 52 weekly.

Payment

Scheduled payment

The monthly instalment, halved for fortnightly or quartered for weekly, then rounded up if you choose.

Extraₖ

Extra paid at period k

Recurring top-ups plus any extra instalment, annual lump sum or one-time prepayment falling due.

Interest saved is the difference between the interest totals of the two simulations, and time saved is the difference between their payoff periods. Because each strategy is simulated independently, they can be combined freely without the estimates drifting.

Assumptions

The interest rate stays fixed and no prepayment or foreclosure penalty applies.
Extra payments reduce the principal immediately and shorten the term rather than lowering the instalment.
Fortnightly and weekly plans are accelerated: you pay half or a quarter of the monthly instalment each period, which adds up to 13 instalments a year rather than 12.
Interest accrues at the annual rate divided by the number of payments per year, so more frequent payments accrue and repay more often.
Extra instalments are spread evenly through the year — one extra falls in month 12, two in months 6 and 12, three in months 4, 8 and 12.
A recurring 'extra per month' is spread across that month's payments, so the yearly total is identical at every frequency.
Lender charges, insurance and taxes are excluded.

Frequently asked questions

Answers about the extra emi impact calculator.

Because the extra payment goes entirely to principal. Your normal instalment is mostly interest in the early years, so only a small slice reduces the balance. An extra payment has no interest to cover, so all of it comes off the principal — and every unit of principal removed early avoids interest for the entire remaining term. On a typical 30-year loan, one extra instalment a year clears it around six years sooner.

Related calculators

Continue exploring adjacent tools in this topic.

Guides that explain this

Background reading on the ideas behind these numbers.

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This tool is provided for educational purposes only. Results are estimates based on the values you enter and do not constitute financial advice.

Strategy

Payoff

Time saved

Interest saved

Outlay / month

15 instalments a yearBest saving

Three extra instalments, four months apart.

17 yrs 5 mo

12 yrs 7 mo

$198,275

$2,489

14 instalments a year

Two extra instalments, six months apart.

20 yrs 1 mo

9 yrs 11 mo

$158,543

$2,324

Extra 10% each month

A steady top-up of a tenth of the instalment.

22 yrs 11 mo

7 yrs 1 mo

$116,640

$2,189

Weekly payments

A quarter of an instalment every week.

23 yrs 9 mo

6 yrs 3 mo

$103,801

$2,162

Fortnightly payments

Half an instalment every two weeks.

23 yrs 9 mo

6 yrs 3 mo

$103,388

$2,160

Annual lump sum

One instalment's worth every twelve months.

24 yrs

6 yrs

$98,548

$2,153

13 instalments a year

One extra instalment every year.

24 yrs

6 yrs

$98,545

$2,153

One-time prepayment

5% of the principal paid in month 12.

25 yrs 11 mo

4 yrs 1 mo

$83,332

$2,042

Round up to 100

Round every instalment up to a neat figure.

29 yrs 10 mo

2 mo

$3,496

$1,997

Assumptions

The interest rate stays fixed and no prepayment or foreclosure penalty applies.

Extra payments reduce the principal immediately and shorten the term rather than lowering the instalment.

Fortnightly and weekly plans are accelerated: you pay half or a quarter of the monthly instalment each period, which adds up to 13 instalments a year rather than 12.

Interest accrues at the annual rate divided by the number of payments per year, so more frequent payments accrue and repay more often.

Extra instalments are spread evenly through the year — one extra falls in month 12, two in months 6 and 12, three in months 4, 8 and 12.

A recurring 'extra per month' is spread across that month's payments, so the yearly total is identical at every frequency.

Lender charges, insurance and taxes are excluded.