Mortgage Repayment Calculator — Ireland 2026

What this mortgage calculator does

This calculator estimates your monthly mortgage repayments, the total amount you will repay over the full term, and the total interest charged. It covers two mortgage structures:

• Repayment mortgage — each monthly payment reduces the outstanding capital and covers the interest charge. By the end of the term you own the property outright. This is the standard structure for residential mortgages in Ireland.
• Interest-only mortgage — your monthly payment covers only the interest. The original loan amount stays unchanged throughout the term and must be repaid separately at the end, typically through an investment vehicle or by selling the property. Interest-only is more common for buy-to-let investors than residential buyers.

Who it is for: First-time buyers working out what they can afford, people trading up or remortgaging, landlords comparing mortgage cost against rental yield, and anyone modelling different rate or term scenarios before speaking to a broker.

What it does not do: This calculator applies a single rate for the entire term. In practice, most Irish mortgages begin on a fixed rate that then reverts to a variable or standard variable rate. Your repayment will change each time your rate changes. Always get a full European Standardised Information Sheet (ESIS) from your lender or broker before making any commitment.

How the mortgage repayment calculation works

A standard repayment mortgage uses the annuity formula, which calculates a fixed monthly payment that ensures the loan is fully repaid by the end of the term. The formula is:

For example, a €340,000 mortgage at 4.5% over 30 years gives r = 0.045 ÷ 12 = 0.00375 and n = 360. Plugging in: PMT = 340,000 × [0.00375 × (1.00375)^360] ÷ [(1.00375)^360 − 1] = €1,723 per month.

Amortisation — how each payment splits between principal and interest

In the early years, most of each payment is interest. As the balance falls, a larger proportion of each payment chips away at the principal. This is amortisation. On a 30-year mortgage at 4.5%, roughly 56% of your first year's payments go to interest. By year 25, over 80% goes to principal reduction.

Interest-only calculation

For interest-only, the calculation is simply: Monthly interest = (P × r). There is no amortisation. The monthly payment stays constant throughout the term (assuming the rate stays fixed), but you make no progress on repaying the capital.

Stress-testing your rate

The European Banking Authority and Irish lenders require that you can afford repayments at a rate 2% higher than your approved rate. This calculator shows what your payment would be if rates rose by 2% — if that stretched repayment would exceed about 35% of your net monthly income, consider borrowing less or extending the term.

Worked examples — Ireland 2026

How to interpret your mortgage result

The true cost of borrowing

The headline monthly repayment is only part of the picture. The total interest figure tells you the real cost of the mortgage. On a typical 30-year Irish mortgage, you will pay roughly 65–90% of the original loan amount again in interest alone — which is why shortening the term or making overpayments has such a large impact.

LTV and your rate

Irish lenders price mortgages in LTV bands. Borrowers below 60% LTV get the best rates — typically 0.5–1% lower than those at 90% LTV. If your LTV is borderline between two bands, consider whether increasing your deposit to drop into the lower band is financially worthwhile over the full term.

Stress-testing at +2%

Regulators require lenders to check that you can afford repayments at your mortgage rate plus 2%. Use this calculator to run your own stress test: enter your rate plus 2% and see how much the monthly payment rises. If the stressed payment would push your mortgage costs above 35% of net household income, you are in a vulnerable position should rates rise.

The impact of overpaying

Even modest monthly overpayments substantially reduce total interest. On a €350,000 mortgage at 4.5% over 30 years, overpaying €100/month saves approximately €24,000 in interest and cuts the term by 2.5 years. Most fixed-rate products allow overpayments of up to 10% of the balance per year without break fees.

Common mistakes when calculating mortgage costs

1. Forgetting the upfront costs

Many first-time buyers focus entirely on the monthly repayment and deposit, forgetting that they also need to fund stamp duty (1% of the purchase price on residential property), legal fees (€1,500–€3,000 plus VAT), a valuation and survey, and mortgage protection insurance. On a €400,000 purchase, these ancillary costs can reach €8,000–€12,000.

2. Calculating affordability on the fixed rate only

A 3-year fixed rate at 3.8% is appealing — but what happens in year 4 when it reverts to the standard variable rate, which could be 5.5% or higher? Model both scenarios before committing to a loan size. The difference on a €350,000 mortgage between 3.8% and 5.5% is over €330/month.

3. The interest-only trap

Interest-only keeps monthly costs low but builds zero equity. After 20 interest-only years on a €280,000 mortgage, you still owe €280,000. If property values have not risen enough to cover the outstanding balance plus transaction costs when you sell, you could be left with a shortfall. Ensure you have a robust repayment vehicle in place before choosing interest-only.

4. Not accounting for term reduction on remortgaging

When you remortgage at the end of a fixed period, some borrowers take a new 25-year term even though they only have 22 years left on the original. This lowers the monthly payment but significantly increases total interest. Always remortgage to the same remaining term unless you have a specific financial reason to extend.

5. Comparing mortgages on headline rate rather than APRC

The Annual Percentage Rate of Charge (APRC) includes arrangement fees and other costs in the comparison figure. A mortgage with a slightly higher rate but no fees can be cheaper overall than one with a low rate and a €1,500 arrangement fee, especially on shorter fixed terms.