Finance Calculator

Mortgage Repayment Calculator

Estimate your mortgage repayments, total interest and overall repayment cost based on your loan amount, interest rate, loan term and repayment frequency.

  • Estimate regular repayments
  • See total interest
  • Compare repayment frequencies
Calculate My Repayments
Mortgage Calculator

Calculate Your Mortgage Repayments

Enter your mortgage details to estimate your regular repayment, total interest and overall cost of the loan. You can also add an extra repayment to see how it may affect your interest cost and payoff time.

Your Mortgage Details

Adjust the figures below to match the mortgage you want to estimate.

$
%
Annual interest rate
years

Extra repayments

Add an optional amount to each regular repayment to estimate how much interest and time you could save.

$

Estimated Repayments

Based on the mortgage details entered.

Estimated regular repayment

$2,997.75

per month

Principal borrowed $500,000.00
Total interest $579,190.95
Total repayments $1,079,190.95
Estimated payoff time 30 years

Repayment breakdown

Principal 46.3%
Interest 53.7%

Estimated benefit of your extra repayments

Interest saved $0.00
Time saved —

Estimate only. This calculator assumes a constant interest rate and regular principal-and-interest repayments. Actual lender calculations, fees, rate changes, taxes, insurance, offset accounts and other mortgage features may change the amount you pay.

Calculation Method

How the Mortgage Calculation Works

The calculator uses the standard principal-and-interest repayment formula to estimate the regular payment needed to repay a mortgage over the selected loan term.

Repayment Formula

Regular Principal-and-Interest Repayment

M = P × r × (1 + r)n (1 + r)n − 1

This formula calculates the level repayment required for the mortgage balance to reach approximately zero after the selected number of repayment periods.

M = regular repayment amount
P = principal, or initial loan amount
r = interest rate per repayment period
n = total number of repayment periods
Rate & Frequency

Converting the Annual Rate

r = Annual interest rate Payments per year

The calculator converts the annual rate into a periodic rate according to the repayment frequency selected. It then multiplies the loan term by the number of repayments per year to determine the total number of periods.

12 = monthly repayments per year
26 = fortnightly repayments per year
52 = weekly repayments per year
n = years × repayments per year

What if the interest rate is 0%?

When the annual interest rate is zero, the standard repayment formula would involve division by zero. Instead, the calculator simply divides the principal by the total number of repayments.

Worked Example

$500,000 Mortgage at 6% for 30 Years

Suppose you borrow $500,000 at an annual interest rate of 6% and make monthly principal-and-interest repayments over 30 years.

Loan amount $500,000
Annual rate 6%
Loan term 30 years
Frequency Monthly
1
Convert the annual interest rate to decimal form 6 ÷ 100 = 0.06
2
Calculate the monthly interest rate 0.06 ÷ 12 = 0.005
3
Calculate the total number of repayments 30 years × 12 monthly repayments = 360 repayments
4
Apply the repayment formula M = 500,000 × [0.005 × (1.005)360] ÷ [(1.005)360 − 1]
5
Estimate the total amount repaid $2,997.75 × 360 ≈ $1,079,190
6
Estimate total interest $1,079,190 − $500,000 ≈ $579,190
Estimated monthly repayment Before fees, rate changes and other mortgage features
$2,997.75
Reading Your Results

Understanding Your Mortgage Calculator Results

Your results show more than the amount due each repayment. They also help illustrate how much of the mortgage is the original amount borrowed, how much may be paid in interest, and how long repayment could take.

01

Regular Repayment

This is the estimated amount paid each week, fortnight or month, depending on the repayment frequency selected. If you enter an extra repayment, the displayed payment includes that additional amount.

02

Principal Borrowed

Principal is the starting mortgage balance entered into the calculator. It does not include interest that may accumulate over the life of the loan.

03

Total Interest

This is the estimated interest paid over the calculated repayment period. A longer term or higher interest rate will generally increase the total interest cost.

04

Total Repayments

This is the estimated total amount paid toward the mortgage, including both principal and interest, based on the assumptions entered into the calculator.

05

Estimated Payoff Time

This estimates how long it takes for the mortgage balance to reach zero. Extra repayments can shorten this period when they are applied consistently.

06

Interest & Time Saved

When an extra repayment is entered, the calculator compares that scenario with the original scheduled mortgage to estimate the interest and repayment time potentially saved.

The Big Picture

Principal and Interest Make Up Your Total Cost

The amount borrowed is only one part of the total cost of a mortgage. Interest is charged on the outstanding balance over time, so the cumulative interest can become substantial on a long-term loan. The repayment breakdown helps you see the estimated proportion of total payments attributable to principal and interest.

Example: $500,000 at 6% over 30 years

Principal ≈ 46.3%
Interest ≈ 53.7%

Why Extra Repayments Can Make a Difference

An extra repayment reduces the outstanding principal faster. Because future interest is then calculated on a smaller balance, consistently paying more than the scheduled repayment can reduce both the estimated total interest and the time needed to repay the mortgage. Actual results depend on your lender’s terms, interest calculations and whether additional repayments are permitted or restricted.

Mortgage Examples

How Rates and Loan Terms Change Your Repayments

Small differences in the interest rate or repayment term can produce substantial differences over the life of a mortgage. These examples use a $500,000 loan with monthly principal-and-interest repayments.

Example 1

The Effect of Different Interest Rates

Here the loan amount and 30-year term stay the same. Only the annual interest rate changes.

30-Year Mortgage

5% Interest

Loan amount $500,000
Monthly repayment ≈ $2,684
Total interest ≈ $466,279
Total repayments ≈ $966,279
30-Year Mortgage

6% Interest

Loan amount $500,000
Monthly repayment ≈ $2,998
Total interest ≈ $579,191
Total repayments ≈ $1,079,191
30-Year Mortgage

7% Interest

Loan amount $500,000
Monthly repayment ≈ $3,327
Total interest ≈ $697,544
Total repayments ≈ $1,197,544

What this example shows

With the same $500,000 balance and 30-year term, increasing the rate from 5% to 7% raises both the regular repayment and the estimated lifetime interest cost. The effect compounds because interest is charged throughout a long repayment period.

Example 2

The Effect of Different Loan Terms

This time the loan stays at $500,000 and the interest rate stays at 6%. Only the repayment term changes.

6% Interest

15 Years

Loan amount $500,000
Monthly repayment ≈ $4,219
Total interest ≈ $259,471
Total repayments ≈ $759,471
6% Interest

20 Years

Loan amount $500,000
Monthly repayment ≈ $3,582
Total interest ≈ $359,717
Total repayments ≈ $859,717
6% Interest

30 Years

Loan amount $500,000
Monthly repayment ≈ $2,998
Total interest ≈ $579,191
Total repayments ≈ $1,079,191

The repayment-term trade-off

A shorter loan term produces a higher regular repayment but generally reduces the amount of time interest accrues. A longer term lowers the scheduled repayment but can substantially increase the total interest paid if the rate and other assumptions remain unchanged.

Examples are estimates and assume a constant interest rate, monthly principal-and-interest repayments and no fees, offset account, redraw effects or other loan features. Figures are rounded for readability.

Repayment Factors

What Affects Your Mortgage Repayments?

Your mortgage repayment is influenced by more than the amount you borrow. Interest rates, the loan term, repayment frequency and additional payments can all affect how much you pay and how long the mortgage lasts.

Loan Amount

The principal is the amount initially borrowed. Increasing the loan amount generally increases both the regular repayment and the total interest paid, assuming the other loan settings remain unchanged.

Higher balance → generally higher repayments

Interest Rate

The interest rate determines how much interest is charged on the outstanding balance. Even a relatively small rate change can materially affect repayments and lifetime interest on a large, long-term mortgage.

Higher rate → higher borrowing cost

Loan Term

Spreading a mortgage over more years usually reduces the scheduled repayment, but interest has more time to accumulate. A shorter term generally requires larger repayments but can reduce total interest.

Longer term → usually lower repayment, more interest

Repayment Frequency

Mortgages may allow monthly, fortnightly or weekly repayments. The calculator adjusts the periodic rate and number of repayment periods to match the frequency you select.

Frequency changes the repayment schedule

Extra Repayments

Paying more than the scheduled amount can reduce the outstanding principal faster. That may reduce future interest and shorten the repayment period, subject to the terms and conditions of the mortgage.

Extra principal → potential interest and time savings

Fees & Loan Features

Application fees, ongoing fees, offset accounts, redraw facilities and other features can affect the real cost of a mortgage. These items are not included in the calculator’s standard repayment estimate.

Compare total loan costs, not only the repayment
Rate Changes

Interest Rate Changes Can Have a Large Effect

On a variable-rate mortgage, repayments may change when the applicable interest rate changes. For example, using a $500,000 balance with 30 years remaining, increasing the annual rate from 6% to 7% raises the calculated monthly principal-and-interest repayment from about $2,998 to about $3,327 under this calculator’s assumptions.

Example — $500,000 with 30 years remaining

Monthly repayment at 6% ≈ $2,998
Monthly repayment at 7% ≈ $3,327
Approximate increase ≈ $329/month
Extra Repayments

How Extra Repayments Can Reduce Mortgage Interest

Paying more than the scheduled mortgage repayment can reduce the outstanding principal sooner. That can mean less interest over time and an earlier mortgage payoff, depending on the loan’s terms and conditions.

Why It Works

A Smaller Balance Can Mean Less Future Interest

Interest is calculated from the outstanding mortgage balance. When an additional payment is applied to principal, the balance falls faster than it would under the original repayment schedule. With a smaller balance remaining, less interest may accrue in later periods.

1
Make the scheduled repayment The regular repayment covers interest and reduces part of the principal.
2
Add an extra repayment The additional amount reduces the mortgage balance faster when it is applied to principal.
3
Reduce future interest Future interest is then calculated from a lower outstanding balance under the calculator’s model.
Example

Adding $200 to a $500,000 Mortgage

Using the same example as earlier — a $500,000 mortgage at 6% over 30 years — compare the standard monthly repayment with paying an additional $200 each month.

Standard Schedule

No Extra Repayment

Regular monthly repayment ≈ $2,997.75
Estimated payoff time 30 years
Estimated total interest ≈ $579,191
Extra Repayment Scenario

+ $200 Each Month

Total monthly payment ≈ $3,197.75
Estimated payoff time ≈ 25 years 6 months
Estimated total interest ≈ $478,218
Estimated interest saved ≈ $100,973
Estimated time saved ≈ 4 years 6 months

Check Your Mortgage Terms First

Extra repayments do not work identically with every mortgage. Before relying on an estimated saving, check how your lender treats additional payments and whether any restrictions or charges apply.

Check whether your mortgage permits additional repayments and whether limits apply.

Confirm that extra payments are applied to the outstanding principal as expected.

Check for prepayment charges, early repayment fees or other conditions that may apply.

Remember that future rate changes can alter the actual interest and payoff time.

Test an Extra Repayment

Enter an additional amount in the calculator to compare the estimated interest and payoff time.

Calculate Extra Repayments
Repayment Schedule

Monthly, Fortnightly or Weekly Mortgage Repayments?

Repayment frequency determines how often mortgage payments are made. This calculator can estimate monthly, fortnightly or weekly repayments using a consistent calculation method for each selected schedule.

Monthly Repayments

12 repayments per year

Monthly repayments are made once each month. The calculator divides the annual interest rate by 12 and calculates the repayment across 12 periods per year.

Fortnightly Repayments

26 repayments per year

Fortnightly repayments occur every two weeks. The calculator uses 26 repayment periods per year and converts the annual interest rate to a corresponding periodic rate.

Weekly Repayments

52 repayments per year

Weekly repayments are made once each week. The calculator uses 52 repayment periods per year when estimating the required payment.

Example Comparison

$500,000 Mortgage at 6% Over 30 Years

Using the calculator’s frequency-specific method, the repayment amount changes according to how many payments are made each year. The figures below are approximate.

Frequency Payments / Year Payment Approx. Annual Total
Monthly 12 ≈ $2,997.75 ≈ $35,973
Fortnightly 26 ≈ $1,382 ≈ $35,932
Weekly 52 ≈ $691 ≈ $35,932

More Frequent Does Not Automatically Mean You Are Paying More

Choosing fortnightly or weekly in this calculator does not simply divide the monthly repayment by two or four. Instead, the calculator independently calculates the repayment required for 26 or 52 periods per year. Therefore, changing the frequency alone should not be confused with deliberately making accelerated or extra repayments.

Important Difference

What Is an Accelerated Fortnightly Repayment?

One commonly described repayment strategy is to take half of a monthly repayment and pay that amount every two weeks. Because there are 26 fortnights in a year, this produces 26 half-payments — equivalent to 13 full monthly payments rather than 12. The additional amount paid during the year is what can accelerate repayment; it is not simply the change from monthly to fortnightly frequency.

Example monthly repayment $2,997.75
Half of monthly repayment ≈ $1,498.88
26 half-payments per year ≈ $38,971
Equivalent full monthly payments 13 per year

Compare Repayment Frequencies

Switch between monthly, fortnightly and weekly in the calculator to compare the estimated payment for your mortgage.

Compare Repayments
Before You Rely on the Estimate

Important Assumptions & Limitations

This calculator is designed to provide a useful mortgage repayment estimate, not an exact lender quote. Understanding the assumptions behind the calculation helps you interpret the results correctly.

Calculator Assumptions

What the Estimate Assumes

The standard repayment calculation is based on the following simplified assumptions.

✓
Principal-and-interest repayments Each scheduled repayment covers interest and reduces part of the outstanding principal.
✓
Constant interest rate The entered annual interest rate is assumed to remain unchanged throughout the modeled period.
✓
Regular repayments Payments are assumed to be made on schedule at the selected monthly, fortnightly or weekly frequency.
✓
Simplified periodic interest rate The annual rate is divided by the number of repayment periods per year for the calculator’s periodic repayment formula.
✓
Extra repayments remain consistent If an extra repayment is entered, the calculator assumes that amount is added to each scheduled repayment until the mortgage is repaid.
Not Included

What the Calculator Does Not Model

Real mortgage costs can differ because lenders and mortgage products may include features not represented by this simplified calculation.

×
Future interest-rate changes Variable-rate increases or decreases are not forecast by the calculator.
×
Mortgage fees and charges Establishment, application, service, annual, discharge and other lender charges are excluded.
×
Taxes, insurance and property costs Property taxes, insurance, rates, maintenance and other homeownership expenses are not included.
×
Offset and redraw features The effect of money held in an offset account or withdrawn through a redraw facility is not modeled.
×
Lender-specific calculation methods A lender may calculate interest using daily balances, different compounding conventions, payment dates or other product-specific rules.
Why Results May Differ

Your Lender’s Figure May Not Be Identical

Mortgage products and calculation conventions vary. The calculator is intended for comparison and planning, so a lender’s repayment figure may differ slightly — or materially where the actual mortgage includes changing rates, fees or additional features.

Interest Timing Interest may be calculated from daily balances rather than using the calculator’s simplified periodic model.
Rate Changes Variable rates can change during the mortgage term, altering future repayments and interest.
Loan Features Offset, redraw, interest-only periods and other features can change the actual repayment path.
Fees & Charges Mortgage fees can increase the real cost even when the advertised interest rate appears lower.

Estimate Only — Not Financial Advice

The results are general estimates for informational and educational purposes only. They are not a loan offer, repayment quote, credit assessment or financial advice. Before making a borrowing or refinancing decision, confirm the applicable rate, repayment amount, fees, features and conditions with the relevant lender or a suitably qualified professional. See our Financial Disclaimer for more information.

Calculate Your Mortgage

See What Your Mortgage Could Cost

Enter your loan amount, interest rate and loan term to estimate your regular repayments, total interest and overall repayment cost. You can also compare repayment frequencies and see the potential effect of extra payments.

Estimate repayments See total interest Test extra repayments
Calculate My Mortgage

Free to use. No sign-up required. Results are estimates for informational and educational purposes.

Frequently Asked Questions

Mortgage Repayment Calculator FAQ

Find answers to common questions about mortgage repayments, interest, loan terms, repayment frequency and extra payments.

How are mortgage repayments calculated?

For a standard principal-and-interest mortgage, repayments can be estimated using an amortization formula based on the loan amount, periodic interest rate and total number of repayments. Each payment covers the interest due for that period and reduces part of the outstanding principal.

How much would a $500,000 mortgage cost per month?

It depends on the interest rate and loan term. For example, a $500,000 mortgage at 6% over 30 years produces an estimated monthly principal-and-interest repayment of about $2,997.75 using this calculator’s assumptions. Fees, rate changes and other mortgage features are not included.

Does a longer mortgage term reduce my repayments?

Generally, yes. If the loan amount and interest rate remain the same, spreading repayment over a longer term usually lowers the scheduled repayment. However, the debt remains outstanding for longer, so the total interest paid can be substantially higher.

How does the interest rate affect mortgage repayments?

A higher interest rate generally increases both the regular repayment and the total interest cost, assuming the loan amount and term remain unchanged. Because mortgages can run for many years, even a relatively small rate difference can have a significant effect on the overall amount paid.

Can extra mortgage repayments save interest?

They can. When an extra payment is applied to the principal, the outstanding balance falls faster. That can reduce the amount of future interest and shorten the payoff period. The actual benefit depends on the mortgage terms, interest rate and how the lender applies additional repayments.

Is it better to pay a mortgage weekly, fortnightly or monthly?

The best schedule depends on the mortgage terms and your payment preferences. Simply changing frequency does not necessarily mean you are paying more toward the mortgage. For example, paying half of a monthly repayment every two weeks creates 26 half-payments per year, equivalent to 13 full monthly payments. In that strategy, the additional annual payment is what can accelerate repayment.

Does this calculator include mortgage fees?

No. The standard estimate does not include application, establishment, annual, service, discharge or other lender fees. It also does not include property taxes, insurance, rates, maintenance or other costs associated with owning a property.

Does the calculator include an offset account?

No. This calculator does not model the effect of an offset account. An offset arrangement can reduce the balance used to calculate interest under the lender’s rules, so the actual interest charged may differ from the estimate shown here.

Why is my lender’s repayment different from this calculator?

Lenders may use different interest-calculation conventions, daily balances, payment dates, rounding methods, fees and product-specific rules. Variable rates, offset balances, redraw activity and other features can also affect the actual repayment or interest charged.

Is this mortgage calculator financial advice?

No. The calculator provides general estimates for informational and educational purposes. It does not provide a loan offer, credit assessment, lender quote or personalized financial advice. Confirm actual repayments, rates, fees and conditions with the relevant lender or a suitably qualified professional before making a financial decision.

Remember: calculator results are estimates

Actual mortgage repayments and costs can vary according to the lender, product structure, interest calculation method, fees, rate changes and other loan features.

References

Sources & Further Reading

We use established mortgage calculation principles and authoritative consumer-finance resources to support the methodology and educational information on this page.

01
Australian Securities & Investments Commission — Moneysmart

Mortgage Calculator

Consumer guidance and calculator information covering principal-and-interest mortgage repayments, repayment frequency, loan terms, interest rates and repayment estimates.

View Moneysmart source
02
Consumer Financial Protection Bureau

How Do Mortgage Lenders Calculate Monthly Payments?

Consumer guidance explaining how principal-and-interest mortgage payments depend on the loan amount, interest rate and loan term.

View CFPB source
03
Consumer Financial Protection Bureau

How Does Paying Down a Mortgage Work?

An explanation of mortgage principal, interest and amortization, including how the balance and the principal-interest split change as a mortgage is repaid.

View CFPB source
04
Australian Securities & Investments Commission — Moneysmart

Mortgage Offset Accounts

Consumer information explaining how an offset account can reduce the mortgage balance on which interest is charged and how offset and redraw arrangements differ.

View Moneysmart source
05
Australian Securities & Investments Commission — Moneysmart

Choosing a Home Loan

Guidance on principal-and-interest loans, loan terms, interest rates, mortgage features and the relationship between repayment size and total interest.

View Moneysmart source

How we use these sources

External sources help us verify calculation principles, terminology, assumptions and explanatory content. The calculator itself uses the methodology described on this page. For more information about how Everything Calculated develops and reviews its tools, see our Methodology .