Free online calculator · Canadian dollars
Compound interest calculator, made simple.
Estimate how a starting balance and monthly contributions could grow over time. See the money you put in, the growth compounding might add, and a range of possible outcomes.
Your starting point
Change any number. The result updates instantly.
What you have today
Your repeatable contribution
Keep the horizon realistic
An assumption, not a promise
Estimated balance in 25 years
$391,147
You contribute
$160,000
Estimated growth
$231,147
The easiest lever to understand
An extra $100 each month could add about $69,299 to the ending balance.
See a range, not a promise
Two percentage points lower or higher changes the picture.
Lower
$284.2K
4% / year
Your estimate
$391.1K
6% / year
Higher
$548.9K
8% / year
How this estimate works
This illustration compounds monthly and adds each contribution at month-end. It assumes a steady return and does not include investment fees, taxes, inflation, or changing contribution amounts. Real returns move around and may be negative.
How to use it
Four inputs. One clear estimate.
Enter what is already invested
Use your current balance, or zero if you are starting fresh.
Add a monthly contribution
Choose an amount you could realistically repeat each month.
Choose a time horizon
Set the number of years the money may remain invested.
Test an annual return
Treat the rate as an assumption and compare the lower and higher scenarios.
Calculation method
How the compound growth estimate works.
Method last reviewed August 24, 2026.
The calculator starts with your current balance. Each month, it applies one-twelfth of the annual return assumption and then adds your monthly contribution. That new balance becomes the starting point for the next month.
next balance = current balance × (1 + annual return ÷ 12) + monthly contribution
With the default example of $10,000 already invested, $500 added monthly, 25 years, and a 6% annual return, the estimate is $391,147. You contribute $160,000 and the remaining $231,147 is estimated growth.
This is an illustration, not a forecast. Real investment returns vary, savings rates change, and losses are possible. The estimate excludes fees, tax, and inflation. The Financial Consumer Agency of Canada explains that compounding frequency affects savings growth; the Bank of Canada also describes its investment calculator results as reference-only.
Common questions
Compound interest calculator FAQ.
What is compound interest?
Compound interest means earning a return on both the money you contributed and the growth already added to it. Over time, that return-on-return effect can become a larger part of the ending balance.
How often does this calculator compound?
This calculator compounds monthly. It divides the annual return assumption by 12, applies that monthly rate to the current balance, and then adds the monthly contribution at month-end.
Does the estimate include inflation, fees, or tax?
No. The result is a nominal illustration before investment fees, taxes, and inflation. Those costs can materially reduce purchasing power and the amount you keep.
Can I use it for a TFSA, RRSP, or savings account?
You can use it to illustrate growth in any account, but it does not model TFSA contribution room, RRSP tax deductions or withdrawals, savings-account rate changes, or account-specific tax treatment.
What annual return should I enter?
There is no universally correct rate. Use a rate that fits what you are modelling, then test several outcomes. A fixed savings product and a diversified investment portfolio have different risks, fees, and expected returns.
Deciding where the money should go? Read the practical guide to TFSA versus RRSP in Canada.