Compound growth calculator
Compound growth rewards time more than almost any other factor in investing. This calculator shows exactly what a starting amount plus steady monthly contributions can turn into, year by year, at a rate of return you choose.
$77,000 contributed, $99,472 earned
Of the $176,472 you end up with, 56% came from growth alone, money you never had to earn or save, just time working on what you put in.
Balance by year, starting today, hover a point for the exact number
A free account keeps your numbers ready across every calculator, no re entering them each time.
How this calculator works
- Step 1Set your starting point
What you have today and what you plan to add each month.
- Step 2Choose an assumed return
A yearly growth rate, stated clearly as an assumption, not a promise.
- Step 3Watch it compound
A year by year chart showing contributions versus growth, out to 30 years.
Frequently asked questions
What is compound interest, in plain terms?
It is growth on your growth. Each year, you earn a return not just on the money you put in, but on every dollar of return you have already earned in prior years. Over enough time, that snowball effect can outweigh your original contributions entirely.
What rate of return should I use in this calculator?
A broad stock market index has historically averaged around 7 to 10 percent a year before inflation over long periods, though any single year can vary widely. This calculator defaults to a conservative assumption you can adjust, since no return is guaranteed.
Does the monthly contribution amount matter more than the starting balance?
Over a long enough timeline, yes, consistent contributions usually end up mattering more than how much you started with. This is exactly why the calculator lets you see both pieces separately in the chart, contributions and growth on top of them.
Why does the chart go out to 30 years?
Compound growth looks unremarkable in the early years and dramatic in the later ones, so a short timeline understates what consistent investing actually does. Thirty years shows the real shape of the curve, especially the acceleration in the final decade.
Is this calculator accounting for taxes or fees?
No, this shows gross growth before taxes, account fees, or fund expense ratios, all of which reduce your real return somewhat. Use it to understand the shape and power of compounding, then account for your specific account type and fund costs separately.
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Every number on this page is a planning estimate, for informational and educational purposes only, not professional advice.
Before you act on any major decisions, consult a qualified accountant, tax advisor, or financial advisor who knows your full picture.