How the Compound Interest Calculator works
See how your money can grow over time. Adjust the inputs above, then use the calculate button to generate a fresh estimate based on the numbers you entered.
The result is designed to give you a quick planning number, plus a short breakdown of the major figures behind it. You can reset the form at any time and try a different scenario.
When to use this calculator
Use this compound interest calculator to estimate how savings or investments may grow when returns are reinvested. It is useful for long-term goals such as an emergency fund, retirement savings, education savings or a general investment plan. The longer the timeline, the more compounding can matter.
Formula
Future value = starting amount x (1 + r)^n plus compounded monthly contributions
- Starting amount is the money already saved or invested.
- r is the periodic return rate.
- n is the number of compounding periods.
- Monthly contributions are added over time and can also earn returns.
Worked example
With $10,000 saved, $500 added each month, a 6% annual return and a 20-year timeline, the calculator estimates the future value and separates contributions from growth.
Common mistakes
- Assuming the same return every year for investments that can rise and fall.
- Forgetting about fees, taxes or inflation.
- Stopping contributions too early and missing the benefit of time.
FAQs
Is the return guaranteed?
No. Savings accounts, GICs and investments all behave differently. Use a realistic rate for the type of account or investment you are modeling.
Why do monthly contributions help so much?
Regular contributions increase the amount working for you, and earlier contributions have more time to compound.
Does this include tax?
No. Tax treatment depends on the account type and your situation.