Compound Interest Calculator
“How much will I have?” “How long until my goal?” “What return do I need?” “How much to invest monthly?”
Answer the four big investing questions for retirement, a 401(k), an IRA, or any savings goal — all with compound interest. You can include an initial lump sum in every calculation.
Just type the numbers, and the result and growth chart update automatically.
This tool has been used … times.
Future Value
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Time Needed
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Required Annual Return
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Monthly Contribution
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* The result recalculates automatically when you change any field.
* Due to rounding, results may differ slightly from actual investment returns.
Enter your initial amount, monthly contribution, annual return, and number of years. The tool calculates your total future balance and breaks it down into principal and earnings, with a growth chart.
Enter your target amount, initial amount, monthly contribution, and annual return to see how many years it takes to reach your goal.
Enter your target amount, contributions, and time frame to find the annual return you need. A binary search computes it with high precision.
Enter your target amount, annual return, and number of years to see how much you need to invest each month. You can also set an initial amount.
What is compound interest, and how is it different from simple interest?
Compound interest means the returns you earn are added back to your principal, so future returns are earned on that larger balance too. Unlike simple interest, which is earned only on the original principal, compound growth snowballs the longer you stay invested. This tool compounds monthly.
How fast does my money double? (The Rule of 72)
The Rule of 72 gives a rough estimate: divide 72 by your annual return (in %). For example, at a 6% return, 72 ÷ 6 = about 12 years to double your money. Use the “Future Value” tab for the exact figure.
How much will my 401(k) or IRA grow to?
On the “Future Value” tab, pick the 401(k) or Roth IRA preset under “Quick presets” to fill in a typical monthly contribution, return, and time frame. Change the numbers to match your own plan to instantly see your projected balance and the split between principal and earnings.
What return and time frame should I use?
Expected returns vary by asset, but for long-term, broad stock-index investing a figure of 6–7% per year (a rough historical average for the U.S. market) is often used as a baseline. This is based on past trends and does not guarantee future returns, so it helps to compare several rates and time frames.