Taking out a loan is one of the biggest financial decisions most people make. Whether it’s a home mortgage, a car loan, or a personal loan, the monthly repayment figure can make or break your budget — yet most borrowers don’t calculate it properly before signing.
This free loan and mortgage calculator gives you the complete picture in seconds: your exact monthly payment, total interest paid over the life of the loan, and the total cost of borrowing. Enter your loan amount, interest rate, and term, and you’ll have everything you need to compare loan options, set a budget, and understand the true cost of debt.
It’s built for first-home buyers, property investors, car buyers, and anyone comparing personal loan offers who wants to make an informed decision before committing.
Use the Calculator
What Is a Loan & Mortgage Calculator (Free) – Calculate Monthly Repayments?
A loan and mortgage calculator is a financial tool that uses the standard amortisation formula to calculate your fixed monthly repayment based on three inputs: the loan principal, the annual interest rate, and the loan term.
Every monthly repayment has two components:
- Principal — the portion repaying the original amount borrowed
- Interest — the lender’s charge for providing the loan
In the early years of a loan, the majority of each repayment goes toward interest. As the loan matures, the balance shifts increasingly toward principal. This is called negative amortisation, and understanding it helps explain why paying even a small amount extra each month can dramatically reduce your total interest paid.
The calculator also accounts for Private Mortgage Insurance (PMI) — an additional cost lenders typically require when your deposit is less than 20% of the property value.
Formula
The standard loan repayment formula is based on compound interest amortisation:
Monthly Payment = P × [r(1+r)ⁿ] ÷ [(1+r)ⁿ − 1] Where: P = Principal loan amount r = Monthly interest rate (annual rate ÷ 12) n = Total number of payments (years × 12) Total Interest = (Monthly Payment × n) − P Total Cost = Monthly Payment × n
Example Calculation
A first-home buyer borrowing $450,000 at 6.5% annual interest over 30 years:
| Loan amount (Principal) | $450,000 |
| Annual interest rate | 6.5% |
| Monthly interest rate | 0.5417% |
| Loan term | 30 years (360 payments) |
| Monthly Payment (P&I) | $2,844.19 |
| Total interest paid | $573,908 |
| Total cost of loan | $1,023,908 |
What Is a Good Result?
Understanding how your loan compares to healthy benchmarks helps you borrow within your means:
| Metric | Safe range | Caution | Risk |
|---|---|---|---|
| Monthly repayment vs income | Under 28% | 28–36% | Over 36% |
| Total debt-to-income ratio | Under 36% | 36–43% | Over 43% |
| Deposit / Loan-to-Value Ratio | 20%+ deposit | 10–20% (PMI) | Under 10% |
| Loan term | 15–20 years | 25 years | 30 years (highest interest) |
How to Reduce Your Loan Cost
Make Extra Repayments
Even **$200 extra per month** on a $450,000 loan at 6.5% over 30 years saves over $100,000 in interest and cuts 5+ years off the loan. Most home loans allow extra repayments without penalty.
Switch to Fortnightly Payments
Paying half your monthly amount every two weeks means you make **26 half-payments per year** — the equivalent of 13 monthly payments instead of 12. This alone can cut years off a 30-year mortgage.
Shop for a Lower Rate
A 0.5% rate reduction on a $500,000 loan saves approximately **$150/month and $55,000 over the life of the loan**. Refinancing is worth calculating whenever rates drop or your credit improves.
Use an Offset Account
An offset account reduces the principal your interest is calculated on. **$50,000 sitting in an offset** against a $500,000 loan at 6.5% saves approximately $3,250 in interest per year.
Choose a Shorter Term
A 20-year term vs a 30-year term on a $400,000 loan at 6% **saves over $120,000 in interest**, though the monthly payment is higher. Calculate whether the saving justifies the budget commitment.
Refinance When It Makes Sense
The break-even point on refinancing is typically **2–3 years**. If you'll stay in the home longer and the rate saving exceeds fees, refinancing almost always wins. Use this calculator to model both scenarios.
Frequently Asked Questions
1How do I calculate my monthly mortgage repayment?
Use the amortisation formula: **Monthly Payment = P × [r(1+r)ⁿ] ÷ [(1+r)ⁿ − 1]** where P is the loan amount, r is the monthly interest rate (annual rate ÷ 12), and n is the total number of payments. The calculator above does this automatically — just enter your loan amount, rate, and term.
2What is the difference between principal and interest, and interest-only loans?
A **principal and interest (P&I) loan** repays both the borrowed amount and interest with each payment. The loan balance decreases over time. An **interest-only loan** only charges interest for a set period — the balance doesn’t reduce. Interest-only loans have lower initial repayments but cost significantly more overall and carry higher risk.
3How much does a 1% interest rate difference cost over the life of a loan?
On a **$500,000 30-year loan**, the difference between 6% and 7% is approximately $330/month and **$118,000 in total interest**. Even small rate differences compound into enormous costs over a 25–30 year term. This is why rate comparison matters.
4Should I choose a 20-year or 30-year mortgage?
A 30-year term gives **lower monthly payments** but costs dramatically more in interest. A 20-year term costs more monthly but builds equity faster and saves tens of thousands. A useful compromise: take the 30-year loan but make 20-year equivalent repayments — you get the security of lower minimums with the savings of faster repayment.
5What is LMI and when do I pay it?
**Lender’s Mortgage Insurance (LMI)** is charged when your deposit is less than 20% of the property value. It protects the lender (not you) if you default. LMI typically costs **1–3% of the loan amount** and can be paid upfront or capitalised into the loan. Saving a 20% deposit avoids this cost entirely.
6How does an offset account reduce my mortgage?
An offset account is a transaction account linked to your mortgage. The balance in the offset **reduces the principal that interest is calculated on**. If you have a $500,000 mortgage and $80,000 in offset, you only pay interest on $420,000. The more you keep in offset, the less interest you pay — without actually making extra repayments.
Conclusion
The true cost of a loan is far more than the monthly repayment. Use the free loan and mortgage calculator above to see your complete repayment schedule, total interest cost, and the impact of extra payments — so you can borrow confidently and repay smarter.