Mathematics & Statistics / Financial Mathematics
Rule of 72 Calculator (Investment Doubling Time)
S&P 500 historical average: ~10-11% annually
About the Rule of 72
Rule of 72: Years to double = 72 / Annual return rate (%)
Reverse: Required rate = 72 / Target years
Exact formula: Years = ln(2) / ln(1 + r)
Example: At 8% return, investment doubles in 72/8 = 9 years
Why 72? It has many divisors, making mental math easier, and it\'s accurate for typical investment returns (6-10%).
See Also
Other calculators in Financial Mathematics