Estimate monthly mortgage repayments
Use the Mortgage Repayment Calculator to compare repayments, interest, and overpayment scenarios.
Quick answer
- The interest rate is one of the biggest drivers of mortgage repayments.
- A small rate difference can have a large monthly impact on bigger loans.
- Fixed rates can give repayment certainty for a set period.
- Variable rates can change, so repayments may rise or fall.
On this page
Why the interest rate matters
The interest rate controls how much interest is charged on the outstanding mortgage balance. A higher rate normally increases the monthly repayment and the total cost of credit over the mortgage term.
Rate sensitivity example
The table below uses a €300,000 mortgage over 30 years.
| Interest rate | Monthly repayment | Difference vs 4% |
|---|---|---|
| 3.00% | €1,265 | €167 lower |
| 4.00% | €1,432 | Baseline |
| 5.00% | €1,610 | €178 higher |
| 6.00% | €1,799 | €367 higher |
Fixed rates vs future repayments
A fixed rate keeps the monthly repayment fixed for the fixed-rate period. This can help with budgeting. When the fixed period ends, the new rate offered by your lender could be higher or lower, so it is worth reviewing options before the end date.
Variable rates and repayment risk
A variable rate can change. If the rate rises, the repayment may increase. If the rate falls, the repayment may reduce. This flexibility may suit some borrowers, but it creates more uncertainty for household budgeting.
Frequently asked questions
How much does 1% add to a mortgage repayment?
It depends on the loan amount and term. On a €300,000 mortgage over 30 years, moving from 4% to 5% increases the example repayment by about €178 per month.
Is a fixed rate safer than a variable rate?
It can provide more repayment certainty during the fixed period, but it may have limits or fees if you overpay or switch early.
Can my repayment change after a fixed rate ends?
Yes. Your repayment may change when the fixed period ends and a new rate applies.
Should I use today’s rate or a stress-test rate?
Use today’s likely rate for a realistic estimate, then test a higher rate to understand affordability risk.
Does the calculator choose a lender rate?
No. You enter the rate yourself and should check lender offers separately.
Is this guide tax advice?
No. It is general information for planning. Use official guidance or a tax adviser for your own situation.
Can I use the calculator for filing?
Use it as an estimate only. Complex activity such as DeFi, staking, mining, business trading, or many swaps may need specialist software or advice.
Sources & references
Key takeaways
- Interest rate changes can materially affect monthly repayments.
- Fixed rates can provide certainty for a period.
- Variable rates can rise or fall.
- Stress-testing a higher rate is useful before committing.