Mortgage Repayment Calculator Ireland: How to Work Out Your Monthly Repayments

Before you fall in love with a house, it pays to know what it will actually cost you every month. A mortgage repayment calculator turns three simple numbers how much you borrow, your interest rate and your term into the one figure that matters most: your monthly repayment. This guide explains how to use a mortgage repayment calculator for Ireland, how the maths behind it works, and how small changes to your loan can save you tens of thousands of euro over the life of the mortgage.

Try it now: Run your own figures with our mortgage repayment calculator for Ireland and get an instant monthly repayment estimate.

What is a mortgage repayment calculator?

A mortgage repayment calculator is a simple tool that estimates the monthly amount you will pay on a home loan. You enter three figures:

• The loan amount – the purchase price minus your deposit.
• The interest rate – the annual rate your lender charges.
• The term – the number of years over which you repay the loan, usually 20 to 35 years in Ireland.

The calculator then works out a fixed monthly repayment that clears both the capital (the amount you borrowed) and the interest by the end of the term. This is known as an annuity or capital-and-interest repayment, and it is how the vast majority of Irish residential mortgages are structured.

It is worth being clear about what the number represents. Your repayment estimate covers the loan itself. It does not include mortgage protection insurance, home insurance, property tax or maintenance all real costs of owning a home that you should budget for separately.

How to calculate mortgage repayments

You do not need to be a mathematician to understand where your repayment comes from. Lenders use a standard formula that spreads the loan and interest evenly across every month of the term:

M = P × [ r(1 + r)ⁿ ] ÷ [ (1 + r)ⁿ − 1 ]

Where:

• M is your monthly repayment
• P is the principal (the amount you borrow)
• r is the monthly interest rate (the annual rate divided by 12)
• n is the total number of monthly repayments (years × 12)

Because early repayments are mostly interest and later ones are mostly capital, the total stays the same each month even though the split changes over time. That is why a mortgage repayment calculator is so useful it does this compounding maths instantly, so you can compare scenarios in seconds rather than working through the formula by hand.

A worked example

Say you borrow €300,000 over 30 years at a fixed rate of 3.5%. Running those numbers through the formula gives a monthly repayment of roughly €1,347.

Over the full 30-year term you would repay about €484,900 in total which means you pay around €184,900 in interest on top of the €300,000 you borrowed. Seeing that interest figure laid out is often the moment borrowers realise why the interest rate and the term matter so much, and why it is worth shopping around before you commit.

How much can I borrow? Understanding the limits

A mortgage repayment calculator tells you what a given loan will cost. Just as important is knowing how large a loan you are actually allowed to take out. In Ireland, the Central Bank sets macroprudential rules that cap most residential lending:

• Loan-to-income (LTI): First-time buyers can generally borrow up to four times their gross annual income. Second and subsequent buyers are capped at 3.5 times.
• Loan-to-value (LTV): First-time buyers need a minimum 10% deposit (a 90% LTV), while second-time buyers also need at least 10%.

Lenders can apply a limited number of exceptions above these limits, but you should plan around the standard rules. A quick way to sanity-check your budget is to work backwards: use a repayment calculator to find a monthly figure you are comfortable with, then confirm the underlying loan sits within your income and deposit limits.

What affects your monthly mortgage repayment?

Three levers move your repayment up or down. Understanding each one helps you use any mortgage repayment calculator more strategically.

The interest rate. Even a small difference matters. In 2026, competitive fixed rates in Ireland sit broadly between 3.0% and 3.8%, with the lowest rates typically reserved for energy-efficient homes (green mortgages) and borrowers with larger deposits. On a €300,000 loan, shaving half a percentage point off your rate can save you well over €25,000 across a 30-year term.

The term. A longer term lowers your monthly repayment but increases the total interest you pay, because you are borrowing the money for longer. A shorter term does the opposite higher monthly cost, far less interest overall. Try the same loan at 25, 30 and 35 years in the calculator to see the trade-off clearly.

The loan amount. The larger your deposit, the smaller your loan, and the lower both your repayment and your total interest. A bigger deposit can also push you into a lower LTV band, unlocking a better interest rate from some lenders.

How long will it take to repay my mortgage?

If you are wondering how long to repay a mortgage, a calculator can answer that from the opposite direction. Instead of fixing the term and solving for the repayment, you fix the repayment you can afford and solve for the term.

For example, on that €300,000 loan at 3.5%, paying the standard €1,347 a month clears it in 30 years. If you could comfortably pay €1,547 a month instead an extra €200 you would clear the same loan in under 24 years and save roughly €42,000 in interest. This is exactly the kind of scenario a good repayment calculator lets you test before you ever speak to a lender.

Using a mortgage early repayment calculator

A mortgage early repayment calculator (sometimes called an overpayment calculator) shows what happens when you pay more than your required monthly amount. Because any overpayment goes straight against the capital, it reduces the balance that future interest is charged on so the benefit compounds over time.

The example above shows the effect: an extra €200 a month on a €300,000 loan can knock around six years off the term and save tens of thousands in interest. Even modest, occasional overpayments a tax refund, a bonus, or rounding your repayment up to the nearest €50 add up meaningfully over decades.

One important caveat for Ireland: if you are on a fixed rate, your lender may charge a break fee for overpaying above an agreed limit. Variable-rate and tracker mortgages can usually be overpaid freely. Always check your loan terms, or ask a broker, before making a large lump-sum overpayment so you do not trigger an unexpected penalty.

From estimate to approval: the next step

A mortgage repayment calculator is the ideal starting point, but it is an estimate, not an offer. The rate you are actually quoted depends on your lender, your deposit, your BER rating, your income and your credit history. Two people borrowing the same amount can end up with very different repayments.

That is where a broker adds value. Instead of checking one bank’s rates, a broker compares offers across the market, factors in the exceptions and green-rate discounts you may qualify for, and helps structure the term so your repayment stays comfortable. The calculator gives you a ballpark; a broker turns it into the best available deal.