How long until your investment doubles, triples, or quadruples – or loses half its value? This growth time calculator tells you how many periods it takes for a quantity to reach a target multiple given a constant growth rate.
Growth Time Calculator
Using the growth time calculator
Select a growth target – Double (2×), Triple (3×), or Quadruple (4×) – then enter your expected Rate per period as a percentage. The calculator instantly shows how many periods it takes to reach that multiple.
The period can be whatever timeframe matches your rate: years, months, days – the math works the same.
The growth time formula
The formula for calculating growth time is:
Where:
t= number of periods to reach the targetn= the growth multiple (2 for doubling, 3 for tripling, 4 for quadrupling)r= the rate per period as a decimal (e.g., 7% = 0.07)ln= the natural logarithm
Deriving the formula
Start with the compound growth formula:
If we want A = nP (the amount to be n times the principal):
Divide both sides by P and take the natural log:
Solving for t:
Example calculations
Doubling at 7% annual return
How long to double an investment growing at 7% per year?
Tripling at 10% annual return
The Rule of 72 (and friends)
The Rule of 72 is a mental math shortcut for doubling time:
At 8%, money doubles in roughly 72 / 8 = 9 years. It's surprisingly accurate for rates between 5-15%.
For tripling, use the Rule of 115: 115 / rate%. For quadrupling, use Rule of 144 (which is just double the doubling time).
Dedicated calculators
For focused tools, try these dedicated calculators:
