Mortgage Calculator – Budget Needs vs Wants

Loan details

Loan entry

Property price

Deposit

Enter deposit in dollars. Tap the toggle to switch to % of price.

Loan amount (outstanding balance)

Already have the loan? Enter the current balance directly — no need to re-enter property price or deposit.

I know my...

"Amount charged" lets you enter the exact interest figure from a statement instead of guessing the rate.

Interest rate (p.a.)

Interest charged last period ($)

Enter the interest amount shown on your statement for one period (matching the repayment frequency below).

Loan type

Loan term

years

Repayment frequency

Split with partner for this calc

▾ Advanced options (extra repayments, offset, future rate)

Extra repayment (optional)

Offset account balance (optional)

Money sitting in a linked offset account. Interest is calculated only on your loan balance minus this amount. In "Amount charged" mode, this adjusts the implied rate rather than the payment — see note below the charge field.

Future rate (optional)

Mortgages saved into your planner from this tool

No mortgages found yet.

Tap a line to select, edit with the calculator, then press “Save / update mortgage in planner”.

Rough guide only. Does not include fees, changing rates, or lender-specific rules.

Your share $0

Results

Enter your loan details and press Calculate to see results.

Your share — Not split

Whole loan repayment: — Per month

Mortgage vs planner surplus

These per-fortnight/per-week figures are the true annualised equivalent of the monthly amount (e.g. monthly ÷ 12 × 26 for fortnightly) — not simply "half the monthly bill". This is the correct steady-state amount to set aside each pay cycle over a full year. However, if your bill is deducted monthly and you're saving fortnightly, keep a small buffer of about one fortnight's contribution sitting in the account before you start relying on it — some months only have one payday before the bill lands (since 26 fortnights ≠ 24 half-months), so a bare $0 starting balance can dip temporarily negative even though the year balances out to zero.

Planner surplus (—) 0

Payment used here 0

Surplus after payment 0

Coverage Run a calculation

Run a calculation to compare. —

Total interest

— ▾

Current rate —

With extra repayments —

Time saved with extra

— ▾

Base term —

With extra —

Future rate comparison

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Repayment at future rate (whole loan) —

Total interest at future rate —

Change vs current —

Enter a future interest rate (in Advanced options) to see how repayments and total interest could change.

Show calculation notes

How this calculator works

Loan amount = property price minus your deposit (or your entered loan balance).
Repayments use a standard amortising loan formula for Principal & Interest, based on your rate, term, and chosen frequency. Interest Only repayments are calculated as simple interest on the balance each period instead.
Extra repayments are added on top of the base repayment and then used to simulate an earlier payoff.
“Your mortgage share” uses your entered split percentage (50/50 by default, adjustable) if the split box is ticked.
“Mortgage vs planner surplus” compares your share to the surplus stored in your main planner for W/F/M/Y.
The future rate view re-runs the same formula at the alternative rate so you can see how sensitive the loan is to rate changes.