Investment Calculator
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See how any amount invested from any age grows over time. Includes real-world examples from age 14 to 50, and encouragement for investors at every stage of life.
Enter your values below and click Calculate for instant results.
One of the most powerful tools in personal finance is compound growth. Money you invest earns a return. That return earns a return. Over decades, this snowball effect creates wealth that feels almost impossible at first, but the math is simple and it works for everyone regardless of starting age or starting amount.
If you are 14 years old and start putting $20 a week into an index fund that returns an average 8% annually, you would have over $147,000 by age 50. You would have contributed less than $37,500 of that. The rest is growth. You did not get smarter or luckier. You just started early and stayed consistent.
This is not a trick. The S&P 500 has returned an average of about 10% annually over long periods. Index funds that track it are available to teenagers through custodial Roth IRA accounts, which parents or guardians can open on behalf of a minor. A teenager with any earned income from a job is eligible to contribute up to $7,000 per year to a Roth IRA in 2026.
If you are reading this at 35 and feel like you missed the window, you have not. Someone who starts investing $300 a month at 35 and earns 8% annually still ends up with over $440,000 by age 65. Someone who starts at 45 with $500 a month ends up with about $295,000. These are life-changing numbers. The best time to start was yesterday. The second-best time is today.
The Rule of 72: divide 72 by your expected annual return to find out how many years it takes your money to double. At 8% return, your money doubles roughly every 9 years. At 10%, every 7.2 years. Money invested at 25 doubles at 34, then again at 43, then again at 52, then again at 61. Each doubling is built on the last one.
People who start investing in their 50s need a different approach. Time is the most valuable ingredient in compounding, and there is less of it. But catch-up contributions, reduced spending, higher monthly amounts, and delaying retirement even a few years can make a meaningful difference. Someone who invests $1,000 a month starting at 52 at 7% return still accumulates about $240,000 by 65. Combined with Social Security and any existing savings, that is a meaningful foundation.
This calculator uses an expected annual return as its variable. A diversified portfolio of low-cost index funds tracking the US stock market has historically returned around 7 to 10% annually over long periods. For most people investing for the long term, a low-cost index fund through a brokerage account, Roth IRA, or 401k is the most straightforward vehicle. Fees matter: a fund with a 0.05% expense ratio versus one charging 1% may seem like a small difference, but over 30 years the fee difference compounds into tens of thousands of dollars.