Mortgage Repayment Calculator

Calculate the Regular Repayment

Comparison only. Enter 0 to use the calculated repayment. Excludes the extra amount above.

Enter 0 for principal and interest from the start. Must be shorter than the remaining term.

A regular principal-and-interest repayment clears the entered balance over the remaining term at the entered rate. Choose monthly, fortnightly or weekly payments before comparing scenarios.

For balance P, periodic rate i and n payments, repayment = P × i ÷ (1 − (1 + i)⁻ⁿ). At zero interest, repayment = P ÷ n.

The default $500,000 loan at 6% over 30 years has 360 monthly payments. The periodic rate is 0.06 ÷ 12 = 0.005. The monthly repayment is $2,997.75.

The first month charges $2,500.00 interest and repays $497.75 principal, leaving $499,502.25. At zero interest, a $1,200 balance over one year needs twelve $100 monthly payments.

An interest-only period initially pays interest on the outstanding interest-bearing balance. Principal falls only through any extra payments. The calculated P&I payment then uses the original principal over the shorter remaining term.

For example, a $1,200 balance at 12% over two years with one interest-only year pays $12 monthly initially. The next year’s calculated monthly P&I payment is $106.62 before extra payments.

Moneysmart’s interest-only calculator describes the same repayment-frequency interest convention. Independently calculated weekly payments differ from dividing a monthly payment by four.

Compare Extra Payments and an Offset

Extra repayments pay down principal. An offset keeps cash in a separate account and reduces the balance used to calculate interest.

The comparison charges periodic interest on the larger of zero and the outstanding loan less the entered offset. An offset above the loan balance earns no interest in this model.

The offset remains available as separate cash and is never deducted from the displayed loan balance. A fully offset loan still needs principal repayments to clear it.

As CommBank’s offset explanation describes, an eligible linked offset account reduces the balance on which interest is charged. This calculation assumes a constant full offset throughout each payment period.

Keep the calculated repayment or enter an alternative P&I amount. Extra repayments are added to that amount. During an interest-only period, extra repayments sit above the period’s interest charge.

The original loan remains visible beside the comparison. A negative interest-saving figure means the alternative costs more interest. A payment that cannot reduce principal is rejected.

The original scenario excludes offset, extra and alternative payments. Both scenarios keep the same entered rate, term and interest-only period.

Read the Loan Amortisation Schedule

Opening balance is the principal before each payment. Interest is added for that period, and payment less interest is the principal repaid. Closing balance carries into the next row.

Higher payments reduce the closing balance faster and can shorten payoff time. The final payment is capped at the remaining debt plus interest. Calculations retain full precision, so displayed rounded columns can differ by a cent.

Enter the remaining term in years or months. For weekly or fortnightly payments, a fractional final period is rounded up to one complete period.

Monthly dates follow the opening day, capped at each month’s last day. Weekly and fortnightly dates advance by seven and fourteen days respectively.

Dated lump sums enter the comparison at the first regular payment on or after their date, after that period’s interest. They never reduce the opening balance immediately.

The lump-sum column records the amount credited at that payment. Amounts are capped at the remaining debt. Sums dated after payoff have no effect.

Tables show the first 120 periods of each scenario. Download both complete schedules as an Excel-compatible CSV with ISO dates and numeric amounts.

The export preserves entered lump-sum dates separately from the schedule dates when they are credited. Payoff time counts complete payment periods and is shown in years.

Original loan

Comparison loan

Interest uses the annual rate divided by payment frequency. The offset stays constant. Fees and daily account movements are excluded. Arithmetic keeps full precision and displays cents.

Use Bank-Branded Calculator Searches

Your entries stay in this tab and clear on reload. The calculator stores no loan data and makes no rate requests.

This calculator uses your assumptions to model repayment arithmetic. It does not use a lender’s current rates or determine borrowing capacity, product eligibility or credit approval.

If you arrive after searching for a Westpac, ANZ, CommBank, CBA, Commonwealth Bank or St George mortgage calculator, enter the rate and term for your own scenario. Bank fees, partial offsets and product restrictions need separate treatment.

The same entered assumptions produce the same arithmetic in Queensland and New South Wales. Actual lender interest can depend on daily balances and the loan contract. This model uses equal payment periods.

For New Zealand, select NZD. Use GBP for a UK scenario and EUR for Ireland. Every entered amount and output keeps that currency without conversion.

All regions use the entered nominal annual rate divided by 12, 26 or 52, with interest compounded at that payment frequency. Daily-accrual contracts can produce different results.

First-home, investment and buy-to-let describe a scenario’s purpose. They do not change this formula or establish eligibility, advertised rates or a product recommendation.

For a proposed property allocation, use the property settlement guide to put the debt scenario beside the asset and liability evidence. Retain both exported schedules when comparing the repayment burden.

Check Loan Percentage and Property Equity

Loan-to-value ratio is secured loan balance divided by property value, multiplied by 100. Equity is property value less that debt.

With a $500,000 balance and a $625,000 property, loan-to-value ratio is 80%. Equity is $125,000, or 20% of property value.

Enter all secured debt in the loan balance when modelling total property equity. An offset remains separate cash and does not reduce secured principal here.

The interest rate measures borrowing cost. Loan-to-value ratio measures debt against property value. A deposit percentage measures the purchase contribution against the purchase price.

Existing equity can reflect repayments or value changes, so it does not establish the original deposit. Negative equity appears when secured debt exceeds property value.

Leave property value blank to omit this optional view. It does not affect repayments or interest in either schedule.