Investment Calculators
Compound interest.
Project investment growth with an initial principal, regular monthly contributions, and any compounding frequency. Includes a year-by-year breakdown table.
Compound interest is growth on both the original amount and the interest already earned: the future value is P(1 + r/n)nt, where P is the starting amount, r the annual rate, n the compounding periods per year and t the years. This calculator adds regular monthly contributions and shows the year-by-year balance.
Source: Bank of Canada — Inflation calculator; Statistics Canada — Consumer Price Index · As of
Cite this page: TNAADO Tools, “Compound Interest Calculator Canada: Monthly Contributions”, https://tools.tnaado.ca/calculators/investment/compound-interest/
Inputs
Future value
Fill the form and press Calculate.
The compound interest formula
A = P(1 + r/n)nt where A is the final amount, P is your principal, r is the annual rate, n is the compounding frequency, and t is the number of years. More frequent compounding nudges the result up slightly; the much bigger lever is time.
Worked example: $10,000 plus $500 a month at 7% for 20 years
Start with $10,000, add $500 at the end of every month and earn 7% a year, compounded monthly, for 20 years. The calculator reports a future value of $300,851. Of that, $130,000 is money you paid in ($10,000 + $500 × 240 months) and $170,851 (56.8%) is growth.
| Compounding | Future value | Total interest earned |
|---|---|---|
| Annually | $284,670 | $154,670 |
| Quarterly | $297,755 | $167,755 |
| Monthly (default) | $300,851 | $170,851 |
| Daily | $302,374 | $172,374 |
- Beyond monthly, frequency adds little. Monthly to daily compounding adds $1,523 (0.5%). The larger gap to annual compounding, $16,181, is partly timing: under annual compounding the page treats a year of deposits as arriving together at year end.
- The monthly deposits do most of the work: with no contributions at all, the $10,000 grows to $40,387 in the same 20 years.
- Nominal is not real: if prices rose 2% a year (an assumption for illustration, not a forecast), $300,851 in 20 years would buy about what $202,464 buys today ($300,851 ÷ 1.0220).
Next steps: check how long it takes your money to double with the Rule of 72 calculator, see a registered-account version in the TFSA calculator or the RRSP calculator, or plan a target age with the retirement calculator.
How this is calculated
The future value of the lump sum is P(1 + r/n)nt, where r is the annual rate, n the compounding periods per year and t the years. Regular contributions are added as an ordinary annuity, paid at the end of each compounding period:
- future value = P(1 + i)N + C × ((1 + i)N − 1) ÷ i
- where i = r ÷ n, N = n × t, and C = monthly contribution × 12 ÷ n is the deposit per compounding period.
- total contributions = P + monthly contribution × 12 × t; total interest = future value − total contributions.
For the default case: i = 0.07 ÷ 12 = 0.5833%, N = 240, so 10,000 × 1.005833240 = $40,387 plus 500 × (1.005833240 − 1) ÷ 0.005833 = $260,463, for $300,851. The rate is whatever you enter; the calculator uses no market data, and it ignores fees, taxes and inflation. To translate a result into today’s purchasing power, use the Bank of Canada’s inflation calculator and Statistics Canada’s Consumer Price Index (both checked 1 October 2026).
An illustration of arithmetic, not a forecast or investment advice. Investment returns are not guaranteed and can be negative.
TNAADO Inc. · Toronto
Compounding is a rate question before it is a time question
Compound growth is the same arithmetic whether the money sits in a GIC or an index fund: the return earned in one period becomes principal for the next. What the curve hides is that the outcome is dominated by the rate and the number of compounding periods rather than by the size of the deposit, which is why a single percentage point of fee difference costs far more over thirty years than almost anyone expects.
The mistake people make. Quoting a nominal return and reading it as purchasing power. A 6% nominal return in a 3% inflation year is a 3% real return, and it is the real figure that decides whether the money buys more later than it does now. Run the nominal result through the Bank of Canada’s inflation calculator before concluding that a plan works.
Frequently asked questions
What is the compound interest formula?
The future value of a lump sum is A = P(1 + r/n)^nt, with P the principal, r the annual rate, n the compounding periods per year and t the years. Regular deposits add a second term, C × ((1 + r/n)^nt − 1) ÷ (r/n). The calculator adds the two.
How much difference does compounding frequency make?
Beyond monthly, very little. On the worked example monthly compounding gives $300,851 and daily $302,374, a gap of $1,523 over 20 years. Annual compounding gives $284,670, lower partly because the page treats a year of deposits as arriving together at year end. A one-point change in the rate moves the result far more.
How much do regular contributions add?
In the example, $500 a month for 20 years puts in $120,000 of your own money and grows to most of the $300,851. The $10,000 starting amount alone reaches $40,387.
Is 7% a realistic return to enter?
The calculator does not know. You supply the rate and it applies it every year without variation. Real investments have good and bad years, and fees reduce what you keep, so run a low, a middle and a high rate before planning around one figure. A guaranteed product such as a GIC and a stock fund have very different risk, so they warrant different inputs.
Does the result account for inflation or tax?
No. The figure is in nominal dollars and before tax. Use the Bank of Canada inflation calculator to see what a future amount is worth in today’s dollars, and the TFSA and RRSP calculators for tax-sheltered growth.
How long does it take to double my money?
Roughly 72 divided by the rate: at 7%, about 10.3 years by the shortcut, or 10.2 years exactly with annual compounding. The Rule of 72 calculator on this site does the check.
Disclaimer
Educational only. Real-world returns vary with market conditions, fees, and taxes. Past performance does not guarantee future results.