Irish Calculators
Loans & mortgages

Mortgage Amortisation and Payment Breakdown Calculator

See how each mortgage payment splits between principal and interest, with a chosen rate reset if needed. Property tax, insurance and other housing costs are supplied monthly amounts, not automatic quotes or tax calculations.

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Your numbers

€
Use the principal owed before the next interest period.
%
Monthly interest is the annual nominal rate divided by 12. This is not a fee-inclusive APR.
Your figures stay on this device.

How the calculation works

Inspect monthly mortgage interest, principal and balance with an optional single rate reset. Separately supplied tax, insurance and other charges show wider housing outgoings without being added to the mortgage debt.

Payment = P × i / [1 − (1 + i)^−n]; at i = 0, payment = P/n. Interest = balance × i; principal = payment − interest; the last payment clears the balance.

  1. Build the initial schedule

    Calculate the annuity payment from principal, monthly rate and term. Interest is charged on opening balance, and the payment remainder reduces principal.

  2. Apply the rate reset

    If enabled, apply the new monthly rate at the specified payment number. Recalculate payments over the remaining months while retaining the original term end.

  3. Separate housing expenses

    Read mortgage debt service separately from supplied tax, insurance and other monthly charges. Those expenses increase outgoings but do not repay mortgage principal.

Worked example: Interest-free mortgage schedule

Sample inputs demonstrate the method. They are not a forecast or product offer.

The first example has €1,200 principal, twelve months, zero interest and no reset or other housing expenses. Each monthly payment is €100 and total mortgage payments are €1,200, all reducing principal.

Loan balance (€)
1200
Annual nominal interest rate (%)
0
Remaining term (months)
12
Start of first interest period
2026-01-01
Schedule rounding
Full precision; display cents
Rate reset payment number (0 = none)
0
New annual nominal rate
5
Monthly property tax supplied
0
Monthly insurance supplied
0
Other monthly housing charges
0

Expected result

Regular payment
€100.00
Total payments
€1,200.00
Worked example: Rate resets before the first payment

Sample inputs demonstrate the method. They are not a forecast or product offer.

Loan balance (€)
1000
Annual nominal interest rate (%)
0
Remaining term (months)
1
Start of first interest period
2026-01-01
Schedule rounding
Full precision; display cents
Rate reset payment number (0 = none)
1
New annual nominal rate
12
Monthly property tax supplied
0
Monthly insurance supplied
0
Other monthly housing charges
0

Expected result

Total interest
€10.00
Total payments
€1,010.00

Understanding your result

The reset scenario shows the payment effect of a rate change with a fixed remaining term. It does not establish refinancing eligibility or include unentered redemption charges.

Calendar dates label monthly periods rather than introducing actual-day interest. A lender's irregular first payment or rounding policy can produce a different statement.

Questions you might have

Why can the last payment differ?

The final payment clears the outstanding principal and interest. In cent-rounding mode it also absorbs accumulated rounding differences.

Can I use a daily-interest bank statement?

The dates here do not change monthly accrual. A lender using actual-day interest or an irregular first period can produce a different schedule.

Choosing the right inputs

Rate reset payment number (0 = none)
Enter the payment number when the new rate starts, or zero for no reset. The revised payment uses outstanding balance and the remaining original term.
New annual nominal rate
Supply the new annual nominal rate for the scenario. It is an assumption rather than a prediction of future market pricing.
Monthly property tax supplied
Enter a known monthly property-tax allowance for housing outgoings. The calculator does not assess the property's tax liability.
Schedule rounding
Choose full precision or monthly cent rounding. Both display cents, but internal calculations and the final clearing payment can differ slightly.

Common mistakes to avoid

  • Do not enter annual tax or insurance in a field asking for a monthly amount.
  • Do not expect a rate reset to extend the term or add financing charges automatically.

Assumptions to check

  • Regular equal monthly interest periods; no daily or irregular first-period accrual. Start date labels the calendar only.
  • A rate reset recalculates payments over the remaining original term. Property tax, insurance and other monthly housing costs are optional supplied expenses; redemption fees and automatic tax calculations are excluded.

Sources and method

Read our calculation and testing approach.