Quick answer
- Enter the amount you expect to borrow, not the property price or household income.
- Use an annual interest rate and the full remaining mortgage term.
- Read the monthly repayment together with total interest and total repayable.
- Repeat the calculation with changed assumptions instead of treating one result as a quote.
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Before entering figures: choose the question you need answered
Use the Mortgage Calculator when you already have a loan amount to test and want an estimated monthly repayment. If your question is how much you might be able to borrow, start with the Mortgage Affordability Calculator instead.
The repayment calculator does not decide whether a lender will approve the mortgage. Its useful job is narrower: it applies the amount, annual interest rate and term you enter, then shows what those assumptions mean for the repayment and long-term cost.
Step 1: enter the mortgage amount, not the property price
The mortgage amount is the loan balance you want to model. For a purchase, a simple starting calculation is property price minus the deposit you will use. A €400,000 property with a €50,000 deposit means testing a €350,000 mortgage, before confirming lender eligibility and keeping separate money for buying costs.
For a mortgage switch, use the outstanding balance rather than the property’s current value. For an overpayment comparison, begin with the balance and remaining term shown on your latest mortgage statement.
Step 2: use a realistic annual rate and term
| Input | What to enter | Common mistake |
|---|---|---|
| Mortgage amount | The expected loan balance. | Entering the full property price despite having a deposit. |
| Interest rate | An annual percentage that matches the scenario being tested. | Entering the monthly rate, APRC or a promotional cashback figure. |
| Mortgage term | The full proposed or remaining repayment period. | Using an age or fixed-rate period instead of the loan term. |
If you do not yet have a lender quote, run more than one rate. Testing the same mortgage at the initial assumption and at a higher rate shows how sensitive the repayment is to the input; it does not predict what future rates will be.
For an independent input check, the CCPC monthly repayment estimator also asks for the amount borrowed, repayment term and interest rate. Enter the same assumptions when comparing estimates.
Step 3: read all three result figures
| Result | What it means | How to use it |
|---|---|---|
| Monthly repayment | The estimated regular capital-and-interest payment under the inputs. | Compare it with the room in your monthly household budget. |
| Total interest | The estimated interest across the term if the rate and payments followed the scenario. | Compare the long-term cost of different terms. |
| Total repayable | The original mortgage plus the estimated interest. | Use it to avoid choosing solely by the lowest monthly figure. |
These figures describe the same scenario from different angles. Extending the term may lower the monthly repayment while increasing the total interest; shortening it usually does the reverse.
A worked reading of the result: borrowing €300,000 at 4% over 30 years gives an estimated monthly repayment of €1,432.25. Using the unrounded payment across 360 months, total repayable is approximately €515,608.52 and total interest is €215,608.52. The total repayable figure is the mortgage plus interest; it is not the purchase price or the amount you need upfront.
This example assumes the rate stays at 4% for the whole term, monthly payments and no fees or overpayments. A displayed monthly amount is rounded to cents, so multiplying that rounded figure by 360 can differ slightly from the total calculated at full precision.
Step 4: change one input at a time
Keep the mortgage amount and term fixed while comparing rates. Keep the amount and rate fixed while comparing terms. Changing one input at a time makes the reason for a different result clear.
Save or note the scenarios you can realistically afford, but budget separately for mortgage protection, home insurance, property tax, management fees where relevant, maintenance and one-off buying costs. The calculator cannot assess credit history, income stability, dependants, lender policy or approval in principle.
Once you understand the output, see the worked repayment examples or read the affordability versus repayment comparison.
Frequently asked questions
What amount should I enter in a mortgage calculator?
Enter the mortgage you expect to borrow. For a purchase, that is normally the property price minus the deposit used; for a switch, use the outstanding balance.
Is the interest rate monthly or annual?
Enter the annual interest rate requested by the calculator. Do not divide it by 12 yourself.
Should the term be the fixed-rate period?
No. Use the full proposed or remaining mortgage repayment term, not only the initial fixed-rate period.
Why should I compare total interest?
A longer term can make the monthly payment look lower while increasing the estimated interest paid over the complete term.
Does the result include insurance and buying costs?
No. Budget separately for mortgage protection, home insurance, Stamp Duty, legal and valuation costs, maintenance and other ownership expenses.
Can this calculator tell me whether I will be approved?
No. It estimates repayment from the figures entered and cannot reproduce a lender affordability or credit assessment.
Sources & references
- Central Bank of Ireland: mortgage measures
- CCPC: mortgage monthly repayment estimator
- CCPC: mortgage overpayment calculator
- CCPC: paying extra off your mortgage
- Central Bank of Ireland: mortgage switching
- CCPC: applying for a mortgage
- CCPC: first-time buyer guide
- Citizens Information: taking out a mortgage
- Revenue: Help to Buy Scheme
- Revenue: Help to Buy amount
- Revenue: residential Stamp Duty rates
- First Home Scheme: eligibility
- First Home Scheme: property price ceilings
- Bank of Ireland: mortgage documentation checklist
- AIB: mortgage approval in principle guidance
Related calculators
Use these tools for the numbers behind this guide.