Investment Calculator – Estimate Growth and Future Value
Project portfolio growth with contributions and compare taxable versus tax-advantaged outcomes.
About the Investment Calculator
What is the Investment Calculator?
An investment calculator projects the growth of a portfolio from an initial amount plus regular contributions, and shows the effect of taxes on gains.
Why use this calculator?
It answers the central investment question: how much will steady investing grow to over time, and how much difference a tax-advantaged account makes.
How to use it
- Enter your starting investment and monthly contribution.
- Enter an expected return and the time horizon.
- Add the tax rate you expect on gains.
Formula
FV = initial(1+r)^n + PMT·((1+r)^n − 1)/r
Assumes a constant return and that all gains are taxed once at the end.
Frequently Asked Questions
What return should I assume?
A diversified stock portfolio has historically returned about 7% to 10% a year before inflation, but this is not guaranteed and varies widely.
Why does starting early matter so much?
Compounding rewards time. Money invested decades earlier has far more chances to grow, so early contributions do the heavy lifting.
What is compound interest?
Compound interest is interest earned on both your original money and on previously earned interest. Over time it can make savings grow much faster than simple interest.
What is the difference between nominal and effective return?
The nominal return ignores compounding within the year, while the effective (annualised) return accounts for it. The effective figure is usually higher and better reflects real growth.
How does inflation affect my returns?
Inflation erodes purchasing power. The real return is the nominal return minus inflation, so an investment can grow in dollars yet still lose value in what it can buy.
What rate of return should I assume?
A common long-term assumption for a diversified stock portfolio is about 6% to 8% per year after inflation, but returns vary and are never guaranteed.
Does this account for taxes and fees?
Unless stated, the tool shows pre-tax, pre-fee growth. Subtract your fund expense ratio and expected tax rate to estimate what you keep.
Is this calculator free to use?
Yes. Every calculator on this site is completely free, with no hidden fees, no subscriptions and no limits on how many times you can use it.
How accurate are the results?
We use standard, widely accepted formulas and calculate in your browser using double-precision arithmetic. Results are rounded for readability, so treat them as reliable estimates rather than a guarantee. Real-world factors can vary the true figure.
Can I add this calculator to my own website?
Yes. Open this calculator page and use the "Add to your website" box in the sidebar to copy a ready-made iframe snippet, then paste it into any HTML page.