Explore how your money could grow under a constant return assumption. Watch contributions stack against growth to understand the effect of deposits and assumed growth.
Investment Details
$
$0$500K
$/mo
$0$5K
%
0%20%
years
1 yr50 yrs
Illustration only: monthly compounding and deposits at month end, at a constant non-negative assumed rate. No fees, taxes, inflation, withdrawals or variable market returns. Growth and the gain-to-deposits percentage are not annualized investment performance.
This visualizer separates your deposits from modeled growth under a constant assumed return. Its charts show an illustration, not future market performance.
1
Enter your initial investment
This is the lump sum you're starting with today — a brokerage balance, an inheritance, or simply $0 if you're starting from scratch and plan to build up entirely through monthly contributions.
2
Set your monthly contribution
Enter the amount you plan to add at each month end. Contributions raise the balance directly; the projection then applies the same assumed monthly growth rate to the accumulated balance. It does not model buying prices or dollar-cost-averaging outcomes.
3
Choose an expected annual return
Choose an explicitly hypothetical rate and compare alternatives, including 0%. Small rate changes can materially affect a long projection. No example rate is a promised or personally recommended return.
4
Set your time horizon
Enter how many years you plan to keep investing. Longer horizons dramatically amplify the effect of compounding — the chart makes this visible as the growth curve steepens in later years.
5
Read the charts and export
The stacked bar chart splits your final balance into contributions vs. investment growth, and the line chart tracks portfolio value year by year. Click "Download PDF" to save a copy of your projection.
Math
How Investment Growth Is Calculated
This visualizer combines two separate growth calculations: how your initial lump sum compounds on its own, and how your stream of monthly contributions compounds as each one is added.
n = compounding frequency per year (12 for monthly)
t = number of years
Why the split between contributions and growth matters
Two portfolios can reach the same final balance in very different ways. One might get there mostly through your own deposits; another might get there mostly through market growth compounding on itself. Seeing the stacked bar chart split out "contributions" from "growth" makes it clear how much of your future balance is money you actually saved versus money the market earned for you — and that ratio shifts dramatically the longer your time horizon stretches.
The power of starting early
Because growth compounds on growth, money invested in your first few years has far more time to multiply than money invested in your last few years — even if the total amount contributed is identical. This is why the portfolio-value line typically looks almost flat for the first several years and then curves sharply upward later on: the base of compounded growth needs time to build before its effect becomes visually dramatic. Try shortening the time period in the calculator above to see how much less pronounced that curve becomes.
If you want to model a single lump sum with no ongoing contributions, see the Compound Interest Calculator. If you're working backward from a target amount, the Savings Goal Calculator tells you exactly how much to contribute each month to get there.
FAQ
Frequently Asked Questions
Compound interest is interest earned on both your original principal and on previously accumulated interest. This creates exponential growth — your money earns money on its money.
There is no single return that fits every investment or time period. The displayed rate is an assumption, not a forecast. Compare several inputs including 0%, and account separately for costs and risk. Real returns can be negative; this visualizer accepts non-negative scenarios. The compound-interest tool also accepts negative return assumptions.
Each deposit adds to the balance and may earn growth over its remaining time in the model. The result depends on contribution size, time and the assumed rate. Contributions do not guarantee gains or remove the possibility of investment losses.
A projection you can reproduce
Start with $1,000, contribute $100 at every month end and enter 6% for 10 years. With monthly compounding, the model gives $18,207.33: $13,000 of deposits and $5,207.33 of growth. At 0%, the same deposits produce $13,000.
Here the monthly rate is annual percent ÷ 1,200. Growth is calculated before each month-end deposit. Fees, taxes, withdrawals and inflation are excluded. No market-return sequence is simulated, so a smooth curve does not imply a predictable investment outcome.