Mortgage Repayment Calculator
Calculate your monthly mortgage repayments, total interest paid, and the full amortisation breakdown based on your loan details.
Formula
Principal & Interest Monthly Repayment:
M = P × [r(1 + r)n] / [(1 + r)n − 1]
- M = Monthly repayment
- P = Principal loan amount
- r = Monthly interest rate = Annual rate ÷ 12
- n = Total number of monthly payments = Years × 12
Interest Only Monthly Repayment:
M = P × r
Total Interest Paid (no extra repayments):
Total Interest = (M × n) − P
Assumptions & References
- Interest is compounded monthly and payments are made monthly.
- The interest rate is assumed to be fixed for the entire loan term.
- Extra repayments are applied directly to the principal, reducing the outstanding balance each month.
- For interest-only loans, the full principal remains outstanding at the end of the term and must be repaid or refinanced.
- No fees, charges, or lender's mortgage insurance (LMI) are included in this calculation.
- Formula reference: Standard amortisation formula as used by the Australian Securities and Investments Commission (ASIC) MoneySmart mortgage calculator.
- Reference: ASIC MoneySmart – Mortgage Calculator