A mortgage calculator estimates your monthly repayment, total interest paid and total amount repaid based on the property value, deposit, interest rate and mortgage term. It is an essential planning tool when buying a home, remortgaging or assessing affordability before speaking to a lender.
The key output is the monthly mortgage payment — the fixed amount you will pay each month for the duration of the term. But the total interest figure is equally important, since it reveals the true long-term cost of your mortgage.
A mortgage is a secured loan where the property itself acts as collateral. Your lender calculates a monthly repayment that covers both interest on the outstanding balance and a portion of the principal, so the loan is fully repaid by the end of the term.
The loan-to-value ratio (LTV) is calculated as the mortgage amount divided by the property value. A lower LTV generally gives access to better interest rates, because the lender has more security. Most lenders offer their best rates at 60% LTV or below.
Deposit €60,000 (20%)
Mortgage amount €240,000
LTV ratio 80%
Annual interest rate 4%
Mortgage term 25 years
Monthly rate: 4% ÷ 12 = 0.3333%
Number of payments: 25 × 12 = 300
Monthly payment ≈ €1,265
Total repaid ≈ €379,500
Total interest ≈ €139,500
- Before viewing properties, to set a realistic budget
- When comparing fixed and variable rate mortgage offers
- When considering a larger deposit to reduce monthly payments
- When assessing whether to remortgage at the end of a fixed term
- When planning overpayments to reduce the outstanding balance faster
- Loan-to-Value (LTV)
- The ratio of your mortgage amount to the property value. An LTV of 80% means you are borrowing 80% of the property value and putting down a 20% deposit.
- Deposit
- The upfront amount you pay toward the property purchase. A larger deposit reduces your LTV, typically giving access to lower interest rates.
- Equity
- The portion of the property you own outright. As you repay the mortgage and property values rise, your equity increases.
- Fixed Rate
- An interest rate that stays the same for an agreed period, typically two to five years, giving certainty over monthly payments.
- Variable Rate
- An interest rate that can change over time, usually linked to the central bank base rate. Monthly payments can rise or fall.
- Calculating affordability based on monthly payment alone without considering total interest
- Ignoring arrangement fees, valuation fees and legal costs which add to the true cost
- Choosing the longest term to minimise monthly payments without considering total interest
- Not stress-testing repayments at a higher rate before committing to a variable mortgage
The loan calculator covers general borrowing needs. The APR calculator lets you factor in arrangement fees to compare the true cost across mortgage products. The stamp duty calculator shows you the upfront tax cost of buying property in your country.