Mortgage & Debt Simulator
See what a mortgage really costs and how to pay it off sooner - extra repayments, an offset account, lump sums, interest-only periods and rate changes - then plan the fastest route out of several debts with the snowball or avalanche method.
Mortgage & debt simulation: Example - mortgage and three debts
All amounts in AUD. Plan start 1 Nov 2026. Mortgage: $600,000 at 6% over 30 years, monthly repayments, $25,000 offset. Debts: 3 (avalanche strategy, $300 a month extra). These are illustrative estimates from the assumptions stated, not lender quotes, credit advice or financial advice. Prepared with KJPO, kjpo.com.
Mortgage & debt simulator · AUD
Example figures
Saved in this browser only. Nothing is uploaded.
Mortgage: required repayment $3,597.30, total interest $582,978, payoff Apr 2054. Debts: debt-free Mar 2030, total interest $8,421.
Mortgage
Your mortgage
Everything updates as you typeProperty value$Used for the loan-to-value ratio only.
Loan amount$The balance you owe or plan to borrow.
Deposit$Property value minus loan. Editing it changes the loan.
Loan-to-value ratio%Editing it changes the loan.
Interest rate (per year)%
Loan termyearsWhole years, 1 to 40.
Repayment frequency
Start dateDrives the dates shown. First repayment is one period later.
Repayment type
Principal & interest repays the loan over the term. Interest-only pays just the interest first, so the balance does not fall during that period.
$600,000 borrowed over 30 years, 12 repayments a year.
What if you paid more?
Drag a slider - the results change straight away$/ monthPaid on top of every required repayment.
$Saves $112,053 in interest and 2 years 7 months.
The offset balance is assumed to stay in the account for the whole loan. Both levers leave your required repayment unchanged, so the loan simply finishes earlier. Add one-off lump sums and rate changes further down.
Required repayment$3,597.30a month
Total interest$582,978$695,031 with minimum repayments
Total repayments$1,182,978$600,000 borrowed + interest
Payoff date1 Apr 205427 years 5 months from the start
Interest saved$112,053versus minimum repayments only
Time saved2 years 7 months1 Nov 2056 becomes 1 Apr 2054
Loan-to-value ratio75.0%at or below 80%
Balance reaches 80% LVRAlready thereproperty value assumed constant
Principal versus interest
Where every repayment dollar goesEstimate$1,182,978total repaid
- Principal $600,000
- Interest $582,978
Remaining balance
Balance owing at the end of each yearEstimate- Minimum repayments only
- With your changes
| Year | Minimum repayments only | With your changes |
|---|---|---|
| Start | $600,000 | $600,000 |
| Yr 1 | $592,632 | $591,090 |
| Yr 2 | $584,810 | $581,631 |
| Yr 3 | $576,505 | $571,588 |
| Yr 4 | $567,687 | $560,925 |
| Yr 5 | $558,326 | $549,605 |
| Yr 6 | $548,388 | $537,587 |
| Yr 7 | $537,837 | $524,827 |
| Yr 8 | $526,635 | $511,281 |
| Yr 9 | $514,742 | $496,899 |
| Yr 10 | $502,115 | $481,630 |
| Yr 11 | $488,710 | $465,419 |
| Yr 12 | $474,477 | $448,209 |
| Yr 13 | $459,367 | $429,936 |
| Yr 14 | $443,325 | $410,537 |
| Yr 15 | $426,294 | $389,942 |
| Yr 16 | $408,212 | $368,076 |
| Yr 17 | $389,015 | $344,861 |
| Yr 18 | $368,634 | $320,215 |
| Yr 19 | $346,996 | $294,048 |
| Yr 20 | $324,023 | $266,268 |
| Yr 21 | $299,633 | $236,774 |
| Yr 22 | $273,739 | $205,461 |
| Yr 23 | $246,248 | $172,217 |
| Yr 24 | $217,062 | $136,922 |
| Yr 25 | $186,075 | $99,451 |
| Yr 26 | $153,177 | $59,668 |
| Yr 27 | $118,250 | $17,453 |
| Yr 28 | $81,168 | $0 |
| Yr 29 | $41,800 | $0 |
| Yr 30 | $0 | $0 |
What this means
In plain English- Your required repayment is $3,597.30 a month. You would repay $1,182,978 in total - the $600,000 you borrowed plus $582,978 in interest, about 97 cents of interest for every dollar borrowed.
- Together your extra repayments, offset and lump sums save $112,053 in interest and finish the loan 2 years 7 months earlier - Apr 2054 instead of Nov 2056.
- Because of the offset, interest is charged on $575,000 rather than $600,000 at the start, which avoids roughly $1,500 of interest in the first year. Your repayment stays the same, so the extra goes into paying the loan off sooner. This only holds while the money stays in the offset account.
- Your loan-to-value ratio is 75.0%, at or below the 80% level lenders commonly look for.
- Rates matter: one percentage point higher would change each repayment by $394.51 and add $100,858 to total interest; one point lower would save $102,985.
Where the saving comes from
Interest saved by each lever alonevs minimum repayments- Extra repayments$0 · no time
- Offset account$112,053 · 2 years 7 months
- Lump sums$0 · no time
- All combined$112,053 · 2 years 7 months
The levers overlap (an extra repayment lowers the balance the offset works on), so the combined saving is not the sum of the separate bars.
Interest-rate changes
Test what a rise or fall would doEstimateNo rate changes. Add one to see the effect of the rate moving after a set number of months. Your required repayment is recalculated from the balance at that point.
One-off lump sums
Bonus, tax refund, inheritance...EstimateNo lump sums. Add one to see what a single extra payment does to the interest and payoff date.
Interest-rate sensitivity
Your loan at rates from 4% to 8%Estimate| Rate change | Rate | Repayment | Total interest | Compared with now | Payoff |
|---|---|---|---|---|---|
| -2 points | 4% | $2,864.49 | $377,003 | -$205,975 | 1 May 2055 |
| -1 point | 5% | $3,220.93 | $479,993 | -$102,985 | 1 Nov 2054 |
| Your rate | 6% | $3,597.30 | $582,978 | - | 1 Apr 2054 |
| +1 point | 7% | $3,991.81 | $683,836 | +$100,858 | 1 Sep 2053 |
| +2 points | 8% | $4,402.59 | $780,402 | +$197,424 | 1 Jan 2053 |
- 1 point lower
- Your rate
- 1 point higher
- 2 points higher
| Year | 1 point lower | Your rate | 1 point higher | 2 points higher |
|---|---|---|---|---|
| Start | $600,000 | $600,000 | $600,000 | $600,000 |
| Yr 1 | $589,869 | $591,090 | $592,098 | $592,913 |
| Yr 2 | $579,219 | $581,631 | $583,625 | $585,237 |
| Yr 3 | $568,025 | $571,588 | $574,539 | $576,925 |
| Yr 4 | $556,258 | $560,925 | $564,796 | $567,922 |
| Yr 5 | $543,888 | $549,605 | $554,349 | $558,173 |
| Yr 6 | $530,886 | $537,587 | $543,147 | $547,614 |
| Yr 7 | $517,219 | $524,827 | $531,135 | $536,179 |
| Yr 8 | $502,853 | $511,281 | $518,255 | $523,794 |
| Yr 9 | $487,751 | $496,899 | $504,444 | $510,382 |
| Yr 10 | $471,877 | $481,630 | $489,634 | $495,857 |
| Yr 11 | $455,191 | $465,419 | $473,753 | $480,126 |
| Yr 12 | $437,651 | $448,209 | $456,725 | $463,089 |
| Yr 13 | $419,214 | $429,936 | $438,465 | $444,638 |
| Yr 14 | $399,833 | $410,537 | $418,886 | $424,656 |
| Yr 15 | $379,461 | $389,942 | $397,891 | $403,015 |
| Yr 16 | $358,046 | $368,076 | $375,379 | $379,579 |
| Yr 17 | $335,536 | $344,861 | $351,239 | $354,197 |
| Yr 18 | $311,875 | $320,215 | $325,354 | $326,708 |
| Yr 19 | $287,002 | $294,048 | $297,597 | $296,938 |
| Yr 20 | $260,858 | $266,268 | $267,835 | $264,696 |
| Yr 21 | $233,375 | $236,774 | $235,920 | $229,779 |
| Yr 22 | $204,487 | $205,461 | $201,699 | $191,964 |
| Yr 23 | $174,120 | $172,217 | $165,004 | $151,010 |
| Yr 24 | $142,200 | $136,922 | $125,656 | $106,656 |
| Yr 25 | $108,647 | $99,451 | $83,463 | $58,622 |
| Yr 26 | $73,377 | $59,668 | $38,221 | $6,794 |
| Yr 27 | $36,303 | $17,453 | $0 | $0 |
| Yr 28 | $0 | $0 | $0 | $0 |
| Yr 29 | $0 | $0 | $0 | $0 |
| Yr 30 | $0 | $0 | $0 | $0 |
Each row adds or subtracts the change from your rate and from any rate changes you entered. It shows the effect of a rate moving, not a forecast of where rates will go.
Amortisation schedule
329 repayments, summarised by year| Year | Repayments | Extra + lump sums | Interest | Principal | Balance at year end |
|---|---|---|---|---|---|
| Year 1 | $43,168 | - | $34,258 | $8,910 | $591,090 |
| Year 2 | $43,168 | - | $33,708 | $9,460 | $581,631 |
| Year 3 | $43,168 | - | $33,125 | $10,043 | $571,588 |
| Year 4 | $43,168 | - | $32,505 | $10,662 | $560,925 |
| Year 5 | $43,168 | - | $31,848 | $11,320 | $549,605 |
| Year 6 | $43,168 | - | $31,149 | $12,018 | $537,587 |
| Year 7 | $43,168 | - | $30,408 | $12,759 | $524,827 |
| Year 8 | $43,168 | - | $29,621 | $13,546 | $511,281 |
| Year 9 | $43,168 | - | $28,786 | $14,382 | $496,899 |
| Year 10 | $43,168 | - | $27,899 | $15,269 | $481,630 |
| Year 11 | $43,168 | - | $26,957 | $16,211 | $465,419 |
| Year 12 | $43,168 | - | $25,957 | $17,211 | $448,209 |
| Year 13 | $43,168 | - | $24,895 | $18,272 | $429,936 |
| Year 14 | $43,168 | - | $23,768 | $19,399 | $410,537 |
| Year 15 | $43,168 | - | $22,572 | $20,596 | $389,942 |
| Year 16 | $43,168 | - | $21,302 | $21,866 | $368,076 |
| Year 17 | $43,168 | - | $19,953 | $23,215 | $344,861 |
| Year 18 | $43,168 | - | $18,521 | $24,646 | $320,215 |
| Year 19 | $43,168 | - | $17,001 | $26,167 | $294,048 |
| Year 20 | $43,168 | - | $15,387 | $27,780 | $266,268 |
| Year 21 | $43,168 | - | $13,674 | $29,494 | $236,774 |
| Year 22 | $43,168 | - | $11,855 | $31,313 | $205,461 |
| Year 23 | $43,168 | - | $9,923 | $33,244 | $172,217 |
| Year 24 | $43,168 | - | $7,873 | $35,295 | $136,922 |
| Year 25 | $43,168 | - | $5,696 | $37,472 | $99,451 |
| Year 26 | $43,168 | - | $3,385 | $39,783 | $59,668 |
| Year 27 | $43,168 | - | $953 | $42,215 | $17,453 |
| Year 28 | $17,453 | - | $0 | $17,453 | $0 |
A year here is 12 repayments from the start date. The last repayment is whatever clears the loan, so it can differ from the others by a few dollars. Illustrative only - your lender's statements will differ in small ways.
Scenario comparison
Mortgage comparisons
Change one thing, keep everything else as you set itEstimateWithout extra repayments
Current- Required repayment
- $3,597.30
- Total interest
- $582,978
- Total repayments
- $1,182,978
- Payoff date
- 1 Apr 2054
- Loan length
- 27 years 5 months
The difference$164,286 less interest6 years 8 months sooner
With $500 a month extra
What if- Required repayment
- $3,597.30
- Total interest
- $418,692
- Total repayments
- $1,018,692
- Payoff date
- 1 Aug 2047
- Loan length
- 20 years 9 months
- Without extra
- With extra
| Year | Without extra | With extra |
|---|---|---|
| Start | $600,000 | $600,000 |
| Yr 1 | $591,090 | $584,922 |
| Yr 2 | $581,631 | $568,915 |
| Yr 3 | $571,588 | $551,919 |
| Yr 4 | $560,925 | $533,876 |
| Yr 5 | $549,605 | $514,720 |
| Yr 6 | $537,587 | $494,382 |
| Yr 7 | $524,827 | $472,790 |
| Yr 8 | $511,281 | $449,867 |
| Yr 9 | $496,899 | $425,529 |
| Yr 10 | $481,630 | $399,690 |
| Yr 11 | $465,419 | $372,258 |
| Yr 12 | $448,209 | $343,133 |
| Yr 13 | $429,936 | $312,213 |
| Yr 14 | $410,537 | $279,385 |
| Yr 15 | $389,942 | $244,532 |
| Yr 16 | $368,076 | $207,530 |
| Yr 17 | $344,861 | $168,246 |
| Yr 18 | $320,215 | $126,538 |
| Yr 19 | $294,048 | $82,258 |
| Yr 20 | $266,268 | $35,247 |
| Yr 21 | $236,774 | $0 |
| Yr 22 | $205,461 | $0 |
| Yr 23 | $172,217 | $0 |
| Yr 24 | $136,922 | $0 |
| Yr 25 | $99,451 | $0 |
| Yr 26 | $59,668 | $0 |
| Yr 27 | $17,453 | $0 |
| Yr 28 | $0 | $0 |
| Yr 29 | $0 | $0 |
| Yr 30 | $0 | $0 |
Adding $500 a month saves $164,286 in interest and finishes the loan 6 years 8 months earlier (Apr 2054 becomes Aug 2047). Every $1 of extra repayment avoids about $1.32 of interest, because each extra dollar stops interest being charged on it for the rest of the loan.
Debt strategies compared
Same debts, same $300 a month extra budgetEstimateMinimum repayments
Baseline- Debt-free
- Dec 2031
- Time
- 5 years 1 month
- Total interest
- $13,252
- Total cost
- $58,252
- Cleared first
- Credit card
Debt snowball
Least interest- Debt-free
- Mar 2030
- Time
- 3 years 4 months
- Total interest
- $8,421
- Total cost
- $53,421
- Cleared first
- Credit card
Debt avalanche
Least interest- Debt-free
- Mar 2030
- Time
- 3 years 4 months
- Total interest
- $8,421
- Total cost
- $53,421
- Cleared first
- Credit card
- Minimums only
- Snowball
- Avalanche
| Time | Minimums only | Snowball | Avalanche |
|---|---|---|---|
| 0m | $45,000 | $45,000 | $45,000 |
| 2m | $43,779 | $43,174 | $43,174 |
| 4m | $42,534 | $41,304 | $41,304 |
| 6m | $41,265 | $39,388 | $39,388 |
| 8m | $39,971 | $37,427 | $37,427 |
| 10m | $38,652 | $35,418 | $35,418 |
| 1y | $37,307 | $33,360 | $33,360 |
| 1y 2m | $35,936 | $31,252 | $31,252 |
| 1y 4m | $34,538 | $29,093 | $29,093 |
| 1y 6m | $33,113 | $26,880 | $26,880 |
| 1y 8m | $31,659 | $24,623 | $24,623 |
| 1y 10m | $30,177 | $22,327 | $22,327 |
| 2y | $28,665 | $19,989 | $19,989 |
| 2y 2m | $27,124 | $17,610 | $17,610 |
| 2y 4m | $25,551 | $15,189 | $15,189 |
| 2y 6m | $23,947 | $12,725 | $12,725 |
| 2y 8m | $22,312 | $10,217 | $10,217 |
| 2y 10m | $20,643 | $7,673 | $7,673 |
| 3y | $18,940 | $5,093 | $5,093 |
| 3y 2m | $17,203 | $2,475 | $2,475 |
| 3y 4m | $15,432 | $0 | $0 |
| 3y 6m | $13,624 | $0 | $0 |
| 3y 8m | $11,779 | $0 | $0 |
| 3y 10m | $9,897 | $0 | $0 |
| 4y | $7,976 | $0 | $0 |
| 4y 2m | $6,273 | $0 | $0 |
| 4y 4m | $4,765 | $0 | $0 |
| 4y 6m | $3,232 | $0 | $0 |
| 4y 8m | $1,867 | $0 | $0 |
| 4y 10m | $991 | $0 | $0 |
| 5y | $102 | $0 | $0 |
| 5y 1m | $0 | $0 | $0 |
With these debts snowball and avalanche clear everything in the same order, so they cost the same. Try changing a balance or rate to see them diverge. Either beats minimum repayments, which would cost $4,831 more interest.
How it works
- Enter your property value, loan amount, rate, term and repayment frequency. Deposit and loan-to-value ratio are linked, and you can switch to interest-only repayments for the first few years.
- Drag the extra-repayment and offset sliders. The required repayment, total interest, payoff date, interest saved and time saved update straight away, with a principal-versus-interest chart and a balance chart against minimum repayments.
- Add one-off lump sums and interest-rate changes, and check how sensitive your loan is to rates one or two points either way. Open the amortisation schedule for a year-by-year or repayment-by-repayment view.
- On the Debt freedom tab, list your debts and choose minimum repayments, snowball (smallest balance first) or avalanche (highest rate first), with an extra monthly budget. See the debt-free date, repayment order and monthly balances.
- On the Compare tab, put extra repayments, an offset, higher and lower rates, saved scenarios, and snowball versus avalanche side by side. Print, export CSV, or back up your data as JSON.
Assumptions and method
- Interest is charged on each repayment date at the annual rate divided by the number of repayments a year (12, 26 or 52). This matches daily interest at the annual rate divided by 365 when the balance only changes on repayment dates. Real lenders count actual days and leap years, so small differences are normal.
- Repayments are made at the end of each period. The required repayment is the standard amortisation payment for the balance, rate and remaining periods, rounded to the cent; the final payment is whatever clears the loan.
- Interest-bearing balance is the loan balance minus the offset balance (never below zero). The offset balance is assumed to stay constant for the whole loan and never changes your required repayment.
- Extra repayments are entered per month and spread across the repayments in a month. Lump sums are paid just after the repayment at the month you choose. Neither changes the required repayment, so the loan finishes sooner.
- A rate change applies from the repayment after the month you choose, and the required repayment is recalculated from the balance then over the remaining term. Rate scenarios are what-ifs, not forecasts.
- Debts are simulated monthly: interest is added, then minimums are paid, then any remaining budget goes to the target debt. Minimums freed up by a cleared debt stay in the pool. A debt whose minimum does not cover its interest is flagged, and a plan that does not clear every debt within 50 years is reported as not paid off - never as debt-free.
- Property value is held constant, and fees, insurance, tax, redraw and split-rate loans are not modelled. Results are illustrative estimates, not lender quotes, credit advice or financial advice.
Worked example
- A $600,000 loan at 6% over 30 years with monthly repayments needs $3,597.30 a month and costs $695,031 in interest, ending Nov 2056 when the example starts Nov 2026.
- Keeping $25,000 in an offset account leaves the repayment unchanged but saves $112,053 in interest and brings payoff forward to Apr 2054 (2 years 7 months sooner).
- The three example debts ($45,000 in total) are cleared in 3 years 4 months with the avalanche method and an extra $300 a month, Credit card first, costing $8,421 in interest - $4,831 less than paying only the minimums, which takes 5 years 1 month.
Privacy
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