A loan repayment calculator estimates your repayment from four inputs: the loan balance, interest rate, loan term and repayment frequency. It is a fast way to see how a rate change, a different term or extra repayments would affect your cash flow.
The trick is to use it for scenarios rather than a single number. Enter your exact figures, run at least three versions (current, improved and a stress test), compare total interest alongside the monthly repayment, and if you are refinancing, add switching costs and work out how long the savings take to cover them.
Why use a repayment calculator in 2026?
The RBA lifted the cash rate target to 4.60% on 30 September 2026 (RBA). If your variable rate moves, your repayment changes too, and a calculator is the quickest way to see by how much. NewGen’s calculators and Moneysmart’s mortgage calculator (checked October 2026) are good starting points.
What can a repayment calculator do, and what can’t it?
What it does well:
- Converts balance, rate and term into a repayment estimate.
- Shows how small changes in rate or term shift your monthly cost.
- Lets you compare options before you approach a lender.
What it cannot do on its own:
- Apply every lender’s credit policy and serviceability rules.
- Replace a credit assessment or personal advice.
- Warn you when a low monthly repayment hides a high total cost.
Which inputs matter most?
| Input | Where to find it | Why it matters |
|---|---|---|
| Loan balance | Latest loan statement or app | A guess can make every saving look wrong |
| Interest rate | Loan statement or lender app | Drives most of the repayment |
| Remaining term | Loan contract or statement | A longer term lowers repayments but raises total interest |
| Repayment frequency | Your current setup | Weekly, fortnightly and monthly can produce different totals |
| Offset balance | Offset account | Reduces the balance you pay interest on |
| Fees | Statement or product schedule | Annual fees add to total cost |
Step 1: How do you set your baseline?
Enter your exact current balance, rate, remaining term and frequency into the mortgage repayments calculator. Note your current repayment, how much surplus you have each month after essentials, and your annual fees. If the baseline is wrong, every saving you model afterwards will be misleading.
Step 2: Which three scenarios should you run?
Scenario A: What does a small improvement look like?
Keep the current term and assume a modest rate improvement, such as what your lender might offer if you ask to reprice. This shows low-disruption relief.
Scenario B: What would a refinance or restructure change?
Compare repricing with refinancing, include realistic switching costs, and test structure changes like adding an offset account or splitting the loan. Use the loan comparison calculator to see options side by side.
Scenario C: What happens if rates rise?
Test repayments at a rate a few percentage points higher. APRA expects lenders to assess new loans at least 3 percentage points above the loan rate (APRA APG 223, checked October 2026), so this mirrors how lenders check affordability. If Scenario C leaves you stretched, the structure is probably too aggressive.
Step 3: How do you calculate refinance break-even?
Before switching lenders, use this formula:
Total refinance costs / monthly repayment saving = break-even months
Include discharge and government registration fees, application and valuation fees on the new loan, any break costs if you are fixed, and any change in annual fees. Then test it in the refinancing calculator or Moneysmart’s mortgage switching calculator (checked October 2026).
If you expect to keep the loan well past break-even, refinancing may be worth exploring. If not, repricing or staying put may be better. Moneysmart’s switching home loans guide covers the process.
Step 4: Why compare total cost, not just the monthly repayment?
A lower repayment can come from three places:
- A better rate (usually good).
- A better structure, such as an offset account (often good).
- A longer term (can be expensive).
Check the total interest over your expected hold period and over the full term. If monthly relief improves but total cost jumps, rethink the structure. If both improve, the option is usually stronger.
Extra repayments work in the other direction. Moneysmart’s guide to paying off your mortgage faster shows how small regular extras can cut total interest (checked October 2026).
How should different borrowers read the results?
- First home buyers: test with a conservative buffer and avoid stretching to the maximum, especially in the first couple of years.
- Growing families: model planned changes such as childcare or a period on one income before locking in a structure.
- Refinancers: treat savings as unproven until break-even, fees and features are checked.
- Debt consolidation: if repayments drop, also check total cost, so short-term relief does not become long-term drag.
What are the most common calculator mistakes?
- Using an estimated balance instead of the exact figure.
- Leaving out annual fees and switching costs.
- Comparing loans with different terms as if they were equal.
- Skipping the stress-test scenario.
- Ignoring how an offset balance and extra repayments affect the result.
- Deciding from one scenario only.
What is the next step after using a calculator?
Write down your non-negotiables: a comfortable monthly repayment, the flexibility you need and a 3-year total cost target. For practical ways to bring repayments down, read the home loan repayments guide. When you want your scenarios checked against real lender policy, talk to NewGen about refinancing options. A calculator gives an estimate only; all loans are subject to lender approval.