Estimate how many years it will take to double your investment at a fixed annual interest rate.
Growth Rate
Fixed annual rate of return
Time to Double
Estimated Years10.3 YearsUsing 72 ÷ 7.0%
Mathematical Precision10.24 YearsUsing logarithmic formula
Projection
Today
$10,000
Year 10.3
$20,000
About this calculator
Overview
The Rule of 72 is a simple and effective shortcut to estimate the number of years required to double the invested money at a given annual rate of return.
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Pro Tips
The Rule of 72 is accurate enough for low to moderate interest rates (3% to 15%).
For very high or very low rates, the 'Rule of 69' or 'Rule of 70' might be slightly more precise in continuous compounding.
This rule assumes compound interest, where earnings are reinvested.
It can also be used to estimate how long it takes for the value of money to halve due to inflation (72 / Inflation Rate).
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Fun Facts
Formula: Years to Double ≈ 72 / Annual Interest Rate
