Number & Finance

Mortgage Calculator

Compare equal monthly installment (annuity) and equal principal repayment plans with interest breakdown and full schedule.

How It Works & Methodology

A mortgage is a secured installment loan used to purchase property. Borrowers generally choose between two primary repayment structures: Equal Monthly Installment (Annuity), where the total payment remains constant each month while interest shrinks and principal rises, and Equal Principal, where the principal portion remains constant while monthly payments gradually decrease as remaining interest drops.

1. Annuity Monthly Payment: M = P * [r(1 + r)^n] / [(1 + r)^n - 1] 2. Equal Principal Monthly Payment: M_k = (P / n) + (P - (k - 1) * (P / n)) * r where P = Principal, r = monthly interest rate, n = total months, k = month number. For a monthly nominal APR quote, r = annualRate / 1200. For the Canadian fixed-mortgage semiannual quote, r = (1 + annualRate / 200)^(1/6) - 1. The APR is entered as a percentage.
Key Assumptions & Scope:
  • Fixed-rate estimates use the selected monthly nominal or Canadian fixed-mortgage semiannual convention; lender contracts and daily-interest methods can differ.
  • Schedules round to the selected currency minor units. Country-based values are editable examples, not current market quotes.
  • Excludes property taxes, home insurance, private mortgage insurance (PMI), and lender origination fees.
  • Zero-percent interest edge cases distribute principal evenly without interest charges.

Frequently Asked Questions

What is the main difference between Annuity and Equal Principal repayment?

Equal Monthly Installment (Annuity) keeps your cash outflow identical every month, making personal budgeting predictable. Equal Principal requires a significantly higher initial monthly payment that steadily decreases over time, resulting in less total interest paid over the life of the mortgage.

Which mortgage structure saves more total interest?

For the same principal, positive interest rate and repayment length, equal principal generally reduces total interest by paying down the balance faster. At zero interest the total interest is zero for either method; currency rounding can also make small totals equal.

Does this calculator include escrow and taxes?

No. This calculator isolates the pure principal and interest (P&I) schedule. Local property taxes, homeowner insurance premiums, and HOA fees vary by location and should be budgeted additionally.