How to Calculate a Mortgage Payment: Amortisation Formula and Tips

A mortgage payment depends on the capital, interest rate, and duration. Learn the French amortisation formula and the difference between fixed-rate and variable-rate mortgages in Italy.

French amortisation

In Italy, mortgages are almost universally repaid using the French amortisation method (constant instalment). In this method each payment is equal throughout the loan term, but its composition changes over time: in the first payments, interest predominates; in the last, capital repayment predominates.

The mortgage payment formula

Payment = C × [i / (1 − (1 + i)^(−n))], where C is the financed capital, i is the monthly interest rate (annual rate ÷ 12), and n is the number of payments (years × 12).

Example: mortgage of €200,000 at 3% annual rate for 25 years. i = 0.03/12 = 0.0025; n = 300. Payment = €200,000 × [0.0025 / (1 − 1.0025^(−300))] ≈ €948/month. Total interest paid: €948 × 300 − €200,000 = €84,400.

Fixed-rate vs variable-rate mortgage

  • Fixed rate: payment unchanged for the full term; protection from rate fluctuations; initially higher rate
  • Variable rate (Euribor + spread): payment can rise or fall; risk if rates increase; initially lower rate
  • Mixed rate: switches between fixed and variable at agreed conditions

Effect of the loan term

Increasing the loan term reduces the monthly payment but increases total interest paid. A €200,000 mortgage at 3% over 20 years has a payment of €1,109/month and total interest of €66,200. Over 30 years, the payment falls to €843/month but total interest rises to €103,500.

Early repayment

Since 2007 (Bersani Law), mortgages for purchasing a primary residence signed after 2 February 2007 incur no early repayment penalties. For earlier mortgages or second homes, penalties may exist but are still limited by law.