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Math Calculators
Doubling Time Calculator
Calculate how many periods it takes for a value to double at a fixed percentage growth rate.
Exact doubling time (periods)
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Rule of 70 estimate (periods)
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About the Doubling Time Calculator
Doubling time tells you how many compounding periods it takes for a quantity growing at a fixed percentage rate — such as an investment, a population or a debt — to double in size.
Formula: Periods = ln(2) ÷ ln(1 + rate ÷ 100)
The quick "Rule of 70" (70 ÷ rate) gives a close approximation without needing logarithms, and is popular for mental estimates of investment growth.
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