Put in a starting amount, add a little each month, and see what it becomes. The surprising part isn't what you save — it's how much the growth adds on top.
You invest $1,000 and it earns, say, $70 in a year. Simple enough. But next year, you're earning a return on $1,070 — not just your original $1,000. The growth starts growing too. That's the entire trick, and it's why the curve in the chart bends upward instead of running straight.
Someone who saves $200 a month starting at 25 will almost always end up with more than someone who saves $400 a month starting at 40 — even though the second person puts in more. The extra years of compounding outweigh the bigger contributions. Starting early is the closest thing to free money in personal finance.
Want to know how long money takes to double? Divide 72 by your return rate. At 7%, money doubles roughly every 10 years. At 9%, every 8. It's a back-of-the-napkin trick, not exact math — but it's close enough to be genuinely useful, and it makes the power of a slightly higher return easy to feel.
It depends what you're invested in. A broad U.S. stock index fund has historically returned roughly 10% a year before inflation, or about 7% after inflation — which is why 7% is our default. Bonds return less. A savings account returns less still. If you want a cautious projection, use 5–6%. If you're invested mostly in stocks and don't mind an optimistic estimate, 8% is defensible. The honest truth: nobody knows the future, and any single number is a guess. Run it a few ways.
No — and any calculator that implies otherwise is misleading you. This is a projection based on a steady return every year. Real markets don't work that way; they go up a lot, down sometimes, and sideways often. Your actual result will be bumpier than the smooth curve here, and the final number could land meaningfully above or below the estimate. The calculator is a guide to the shape of things, not a promise.
Monthly. The calculator adds your monthly contribution every month and compounds the balance monthly, which matches how most people actually save — a bit out of each paycheck. If you contribute in one annual lump sum instead, your real result will be slightly different, but close enough that it won't change any decision you'd make.
This calculator shows you the math, not the account. In practice, money you're growing for the long term usually belongs in tax-advantaged accounts first — a 401(k), especially up to any employer match, then an IRA — before a regular taxable brokerage account. The order of accounts matters as much as the picks inside them. We cover this in our investing articles.
It does, and it's worth being clear-eyed about. $1 million in 30 years will buy less than $1 million buys today. One simple way to handle it: use a return rate that already has inflation subtracted out — for stocks, that's roughly 7% instead of 10%. If you use that "real" return, the final number is in today's purchasing power, which is easier to make sense of.
This one shows how money grows in general. Our retirement calculator adds the pieces specific to retiring — your target age, what you'll need, and how long the money has to last.
This calculator produces estimates based on a constant annual return, which real investments do not provide. It is for educational purposes only and is not personalized investment, tax, or legal advice. Past market performance does not guarantee future results, and your actual returns will vary. Consider speaking with a qualified financial professional about your specific situation before making investment decisions.