Investment Calculator

Calculate the future value of your investments with regular contributions and compound growth.

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Initial Investment

Monthly Contribution

Annual Return Rate (%)

Investment Period (years)

Compounding

Annual Inflation Rate (%)

Future Value

Total Contributions

Investment Growth

Return on Investment

Real Value (adj.)

Project the future value of an initial investment plus regular monthly contributions under compound growth, and see how much of the ending balance is your own money versus investment returns.

How It Works

How Investment Calculator Works

Starting from your initial investment, the calculator steps forward one month at a time for the full investment period: each month the balance grows by your annual return rate (divided by 12) and then your monthly contribution is added on top, so both the original investment and every past contribution keep compounding together.

Total contributions is simply the initial investment plus monthly contribution × number of months; investment growth is the ending balance minus that contributed total, and return on investment (ROI) expresses growth as a percentage of what you actually put in.

The ending balance is also shown adjusted for inflation — divided by (1 + inflation rate)^years — to reflect what that future amount would actually be worth in today's purchasing power, and the bar chart splits each year's balance visually into the contributed portion versus the growth portion.

Worked Example

See It In Action

A $10,000 initial investment plus $500/month in contributions, growing at 8% annually for 20 years, reaches a future value of about $343,778. Of that, $130,000 came directly from your own contributions, while roughly $213,778 — a 164.4% return — is pure investment growth. Adjusted for 2.5% annual inflation, that balance is worth about $209,798 in today's dollars.

Real-World Use Cases

Who Uses Investment Calculator and Why

Projecting how an initial lump sum plus ongoing monthly contributions could grow over a multi-year investing horizon.
Seeing what share of an eventual portfolio balance is your own money versus investment growth, expressed as a return-on-investment percentage.
Comparing the nominal future value of an investment against its inflation-adjusted value in today's dollars.
Testing how starting contributions a few years earlier changes the final balance for the same total amount contributed.

Common Mistakes

Mistakes to Avoid

Entering a return rate that doesn't already account for fees or taxes — the calculator takes the return rate at face value, so an unadjusted rate will overstate your realistic ending balance.
Comparing the nominal future value directly to a current-day savings goal instead of using the inflation-adjusted figure, which reflects actual future purchasing power.
Assuming growth and contributions scale the same way — because growth compounds on itself, it can end up outpacing your contributed total the longer the time horizon runs, which isn't a calculation error.

Pro Tips

Tips for Best Results

Use a return rate that already reflects your account's actual fees and expected tax treatment for a more realistic projection.
Compare two runs with the same total contributed amount but different start dates to see concretely how much starting earlier is worth.

Troubleshooting

Fixing Common Problems

My investment growth figure seems disproportionately larger than what I contributed. — This is expected over long horizons — since returns compound on the growing balance every month, not just the original deposit, growth can outpace contributions the longer the investment period runs.

Glossary

Terms Explained

Return on Investment (ROI): Investment growth expressed as a percentage of total contributions, showing how much your money grew relative to what you put in.

Inflation-adjusted value: The future balance restated in today's purchasing power by dividing it by (1 + inflation rate) raised to the number of years.

FAQ

Frequently Asked Questions

Why is "investment growth" so much bigger than my contributions in the example?

Because compounding applies to the growing balance every month, not just your original deposit — over 20 years, returns earned on earlier growth start generating their own growth, which is why the growth portion can end up outpacing total contributions.

Why is the future value shown twice — nominal and inflation-adjusted?

The nominal figure is the actual dollar balance at the end of the period; the inflation-adjusted figure translates that into today's purchasing power, since $1 in 20 years won't buy as much as $1 today.

How much difference does starting earlier really make?

A large one — because growth compounds on itself every month, money invested earlier has more months to compound, so even a few extra years at the start of the period can meaningfully increase the final balance compared to the same total contributed later.

Does the return rate I enter account for fees or taxes?

No — enter the return rate you actually expect to receive on the investment. If your account charges fees or your gains are taxed, use a rate that already reflects those costs for a more realistic projection.