Compound Interest Calculator
Project savings or investment growth over time with regular contributions. Year-by-year breakdown, downloadable CSV.
Runs entirely in your browser. Nothing is sent to our servers.
About this tool
Models how a savings or investment account grows over time with compound interest and regular contributions. Useful for planning RRSP or TFSA growth, projecting retirement savings, evaluating GIC vs. ETF returns, or understanding the impact of starting earlier.
What "compound interest" really means
Each compounding period, the interest earned is added to the balance, so the next period's interest is calculated on a larger base. Over long time horizons this exponential growth dwarfs the initial principal. An RRSP that earns 7% annually doubles roughly every 10 years (the "rule of 72": 72 ÷ rate ≈ years to double).
Realistic return rates
Quick reality check before you punch in 15%:
- 0.5–4% — high-interest savings accounts, GICs
- 3–5% — long-term bond funds
- 6–8% — balanced ETF portfolios, historical average
- 8–10% — equity-heavy ETF portfolios over long horizons
- 10%+ — selective stock picking or speculative assets (high variance, no guarantee)
This tool doesn't model inflation or taxes — both eat returns. A real 7% nominal return is closer to 4–5% in purchasing-power terms.
The schedule
Year-by-year breakdown shows starting balance, contributions made, interest earned, and ending balance for each year. Download as CSV for spreadsheet analysis or your retirement planning records.
Frequently asked questions
- Should I include inflation in the rate?
- This tool uses nominal returns (before inflation). To see real (inflation-adjusted) growth, subtract your inflation estimate from your return rate — e.g. 7% nominal − 2% inflation = 5% real. That gives a more honest picture of future purchasing power.
- What about taxes?
- Not modeled. Taxable accounts pay tax on interest, dividends, and capital gains each year, reducing the compounding base. TFSA growth is tax-free; RRSP growth is tax-deferred until withdrawal. For taxable account modelling, reduce your rate by your marginal tax rate × the proportion that's taxed annually.
- Why does monthly compounding give slightly more than annual?
- Because interest gets added (and starts earning interest itself) more often. The difference is small — usually under 1% over decades — but real. Many advertised "annual rates" use semi-annual or monthly compounding internally.
- Are bi-weekly contributions better than monthly?
- Slightly. Bi-weekly = 26 contributions per year vs monthly = 12, so over a year you contribute either 26 × your bi-weekly amount or 12 × your monthly amount. If both amounts are equivalent annually, the difference is tiny. The main reason to choose bi-weekly is that it matches a typical paycheck cycle.
Last updated: May 17, 2026