Mental math for compounding — close enough to use, fast enough to remember.
infoEducational only. This tool does not provide financial, investment, legal, or trading advice. Trading and investing involve risk. Verify information independently and make your own decisions.
Results
Heuristic — best between 5–10%, slightly off at extremes.
Divide 72 by the annual return to estimate the years required to double an investment under compounding. The calculator returns years to double for the input return.
Years to Double ≈ 72 ÷ Annual Return %
8% annual return → 72 ÷ 8 = 9 years to double. 6% annual return → 12 years.
35 realistic scenarios pause at the decision point — long, short, or stay out. Free in the ChartsQuest quest.
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Sign up freeProject how a starting balance grows with compounding and recurring contributions.
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savingsProject investment value with contributions, returns, and an optional inflation adjustment.
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percentCompute return on investment — net profit, ROI percentage, and annualized ROI.
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Very accurate between 5% and 10% annual returns. Diverges slowly at extremes; for higher returns the Rule of 70 or 69 is closer.
No. Subtract inflation from the return to get a real-return doubling estimate.
There's no right answer — test multiple scenarios rather than fixing on one optimistic number.
No, the tool is free and works without signing in.
Educational only. This tool does not provide financial, investment, legal, or trading advice. Trading and investing involve risk. Verify information independently and make your own decisions.