Doubling Time Calculator
Enter a growth rate per period and how many times bigger you want it to grow.
This result is an estimate only. Double-check important figures before relying on them.
How it is calculated
- Periods = ln(multiple) ÷ ln(1 + rate ÷ 100)
- Doubling time uses a multiple of 2
- Rule of 72 estimate = 72 ÷ rate
For money specifically, use the rule of 72 calculator.
Worked example
Growth of 7% per period:
- Doubling = ln 2 ÷ ln 1.07 = 10.24 periods
- Rule of 72 gives 10.29
Why your number may differ
The result assumes the same growth rate every period. Real populations and prices slow down or speed up.
Frequently asked questions
How do I calculate doubling time?
Doubling time = ln(2) ÷ ln(1 + growth rate). At 7% a period it takes about 10.2 periods.
Can I use another multiple?
Yes. Replace 2 with the multiple you want. Time = ln(multiple) ÷ ln(1 + rate).
How does it compare with the Rule of 72?
The Rule of 72 gives a quick estimate by dividing 72 by the rate. It is close for growth rates between about 5% and 12%.