A regular loan payment is designed to cover the interest due for a period and reduce some principal. The exact result depends on the rate convention, payment frequency, amortization, fees, and lender agreement.
The level-payment formula
For a fixed periodic rate and equal payments, the standard amortization formula uses principal P, periodic rate r, and number of payments n.
Payment = P × r × (1 + r)^n ÷ ((1 + r)^n − 1)Personal and auto loan estimates
A simplified monthly model divides the stated annual rate by 12. Actual agreements can use different compounding, fee, or timing rules, so confirm the annual percentage rate and disclosure documents.
Canadian fixed-rate mortgage convention
Canadian fixed-rate mortgage examples commonly disclose interest compounded twice per year but charged monthly. To estimate a monthly payment, the nominal semi-annual rate must be converted to an effective monthly rate before using the payment formula.
Monthly rate = (1 + annual nominal rate ÷ 2)^(1/6) − 1Term versus amortization
The term is the period covered by the current mortgage contract. Amortization is the planned time to repay the entire balance. A 25-year amortization can include several shorter terms and future rates that are unknown today.
What an estimate leaves out
- Fees, optional insurance, property taxes, and mortgage default insurance
- Changes at renewal or under a variable rate
- Biweekly, accelerated, or extra payments
- Lender-specific rounding and payment dates
- Qualification rules and affordability assessments