Understanding how loan interest works is the first step to making smarter borrowing decisions. Whether you’re taking out a car loan, personal loan, or mortgage, knowing how lenders calculate interest helps you see the true cost of borrowing and compare offers with confidence.
There are two main ways interest can be calculated in Canada: simple interest and compound interest.
Simple interest is calculated only on the original amount you borrowed (the principal). The formula is straightforward:
Interest = Principal × Rate × TimeFor example, if you borrow $10,000 at 5% for 3 years using simple interest:
$10,000 × 0.05 × 3 = $1,500You’ll pay $1,500 in interest over three years, for a total repayment of $11,500.
Compound interest works differently. Interest is charged on both your principal and the interest that accumulates over time. It’s more common for long-term loans and mortgages.
Amount = Principal × (1 + Rate ÷ n)n × TimeWhere n is the number of compounding periods per year. For example, monthly compounding means n = 12.
So, if you borrow $10,000 at 5% compounded monthly for 3 years:
$10,000 × (1 + 0.05 ÷ 12)36 ≈ $11,616That means you’ll pay about $1,616 in interest, slightly more than with simple interest because of compounding.
Try it yourself with our Loan Calculator or Compound Interest Calculator.
In Canada, most lenders quote an annual interest rate (APR). However, interest is usually calculated more frequently, such as monthly, bi-weekly, or even daily, depending on your loan type.
For example:
This means your “5% interest rate” might actually result in slightly more than 5% in total cost once compounding is applied.
| Loan Type | Principal | Rate | Term | Total Interest | Total Cost |
|---|---|---|---|---|---|
| Simple Interest | $10,000 | 5% | 3 years | $1,500 | $11,500 |
| Compound Interest (Monthly) | $10,000 | 5% | 3 years | $1,616 | $11,616 |
This small difference grows over longer loan terms or higher interest rates, which is why understanding compounding matters.
If you know your loan amount, interest rate, and term, you can easily estimate your payment and total cost using our calculators:
These tools automatically handle the math for you so you can focus on comparing offers and planning your budget.
Understanding these basics can save you hundreds or even thousands of dollars over the life of your loan.
You can calculate loan interest using either the simple or compound formula. Simple interest is Principal × Rate × Time, while compound interest applies interest on top of previous interest. Most loans in Canada use compound interest, so using an online loan calculator is the easiest way to get accurate results.
It depends on the loan type. Mortgages are compounded semi-annually by law, even if payments are monthly. Personal and car loans may compound monthly or even daily. Always check your loan agreement to see how often interest is calculated.
Personal loan rates in Canada typically range between 6% and 12% for borrowers with good credit, although they can be higher for unsecured or bad-credit loans. Use a personal loan calculator to see how different rates affect your total cost and monthly payment.