Investment Calculator
See what a starting balance and a monthly habit turn into over time. This is the same compound-growth engine that powers projections inside the WealthTrunk app.
For illustrative purposes only. Not financial, tax, or investment advice.
Real return after inflation: 4.4%. Results are shown in today's money. Set inflation to 0% for future dollars.
Contributions will match inflation.
A projection is only as good as your real numbers. WealthTrunk tracks every account you own, projects them together, and shows your whole net worth in one place.
Try the appHow this calculator works
Growth is applied monthly
Your annual return is converted to a monthly rate — (1 + rate)1/12 − 1 — and applied to the whole balance each month. Compounding monthly rather than annually is what the app does, so the two agree.
Contributions land after growth
Each month's contribution is added after that month's growth is applied, so a fresh contribution doesn't earn a return in the month it arrives. It's the conservative convention.
Contributions can escalate
By default your monthly amount rises with inflation each year and compounds, which tracks saving a constant share of a salary that keeps pace with prices. Move the rate above 0% if you expect real raises on top of that, or below it to grow slower than prices.
The split is what matters
The two stat cards separate what you put in from what the market added. Over long periods the growth typically overtakes the contributions — the crossover point is the interesting part.
Investment calculator FAQ
How is the growth calculated?
Month by month. Each month your balance grows by one month's worth of your annual return — (1 + rate)^(1/12) − 1 — and then your contribution is added. That's the same order the WealthTrunk app uses, so the projection here matches what you'll see in the app for the same inputs.
Are the results adjusted for inflation?
Yes. The inflation slider converts your nominal return into a real return using the Fisher equation — real = (1 + nominal) ÷ (1 + inflation) − 1 — and the projection compounds at that real rate. A 10% return with 2.5% inflation compounds at roughly 7.3%, so the balance is in today's purchasing power. Set inflation to 0% to see future dollars instead.
What does the contribution growth setting do?
It sets how your monthly contribution changes each year, using one rate whose meaning follows the inflation slider above it. While inflation is above 0% the rate is an adjustment against it — labelled ± vs. Inflation — so leaving it at 0% means the contribution rises in line with prices and its buying power stays constant. That's the usual case, and what a fixed percentage of a salary looks like, such as a 401(k) deferral. Set +2% if you expect real raises beyond inflation, or a negative value to grow slower than prices. With inflation at 0% there is nothing to adjust against, so the same slider becomes a plain Annual change and 0% keeps the amount flat. If you're not sure, leave it at 0%.
What return should I use?
That's your call, and it's the assumption that moves the result most. Historical long-run stock market returns have averaged in the 7–10% range before inflation, but any individual decade can be far higher or lower. Try a few rates to see how wide the range of outcomes is.
What does the dashed line show?
Your contributions alone, with no growth applied — your starting balance plus every dollar you put in. The gap between the two lines is the compounding.
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