Model what consistent monthly investing could become. Change the assumptions, watch the gap between "money in" and "money grown" widen.
Set your scenario
This is a sandbox for thinking, not a product recommendation. Pick numbers that feel real to you.
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$
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1 yr60 yrs
Increase contribution over time
Model raises by bumping your monthly amount each year
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Results
Over 20 years
Total value
$0
You contributed
$0
Growth earned
$0
The gap between the lines is compounding doing the work — money your money made, without you adding another dollar.
Before you touch the calculator
Compound interest is growth on your growth — you earn returns not just on what you put in, but on every gain you've already made. That's why the curve bends upward instead of climbing in a straight line: each year's gains become part of next year's base.
Principal is the lump sum you start with. Contributions are what you keep adding over time. Growth is everything above those two — the return your money generates on its own. The calculator's stat cards split your ending balance into exactly these pieces.
The return rate you set here is a smooth average — real markets don't move in a straight line. A "9% average" might mean +22% one year and -8% the next. This tool assumes a constant rate to teach the shape of compounding, not to predict any single year.
Starting early beats starting big. Money invested sooner has more compounding cycles behind it, and each cycle builds on the last — so a few early years can outweigh a much larger contribution made later. Try shifting the time horizon slider and watch how much the ending value moves.
Investing a fixed amount on a regular schedule — like a monthly contribution — means you automatically buy more when prices are low and less when they're high, without trying to time the market. It's less about maximizing any single purchase and more about staying consistent.
Higher potential returns generally come with more short-term ups and downs, not a guarantee of more money. A higher return rate in this calculator isn't "the better setting" — it's a trade-off you'd be accepting in real life, usually in exchange for more volatility along the way.
Every number in this tool is nominal — actual future dollars, not adjusted for inflation or fees. A dollar 30 years from now won't buy what it buys today, so treat the ending balance as a measure of growth, not as today's purchasing power.
Build an emergency fund first — cash for 3-6 months of expenses, kept somewhere accessible.
Know your timeline — money you need in the next couple of years usually doesn't belong in the market.
Understand what you're actually invested in before you put money into it.
Pay down high-interest debt — a guaranteed "return" that's hard for investing to beat.
Only invest what you can leave alone through a downturn.
