Compound interest
Future value of a starting lump sum plus optional monthly contributions with compound growth.
Open calculatorRule of 72
Years to double ≈ 72 ÷ annual return percentage. At an 8% annual return, your money doubles in roughly 9 years.
Constant nominal annual rate in percent — years ≈ 72 ÷ rate.
%
Years to double
10.3
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A mental-math shortcut for compound growth — most accurate for rates between 4% and 12%.
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Educational estimate only. Not medical, tax, legal or financial advice.