Doubling Time Calculator
Calculate doubling time from a growth rate, and the growth it produces over a period.
About Doubling Time Calculator
Doubling time comes from the logarithmic form of compound growth. The rule of 70 approximates it well at low rates and drifts upward as rates rise above about 15 per cent. Doubling time is the most intuitive way to convey exponential growth, whether for bacteria, compound interest or data volumes.
Formula
Doubling Time
t_double = ln2 ÷ ln(1 + r); rule of 70: t ≈ 70 ÷ growth percentage
- rule of 70
- A close approximation for growth rates below about 15%
Worked example
With the default values below, Doubling Time Calculator returns Doubling Time of 9.0065. Change any input above and every figure here is recalculated in your browser.
Inputs used
- Growth rate per periodaccepts 0–500 %
- 8 %
- Number of periodsaccepts 0–1,000
- 24
- Initial quantityminimum 0
- 1,000
Results
- Doubling Time
- 9.0065 periods
- Quantity After the Period
- 6,341.181
- Doublings Achieved
- 2.6648
- Rule of 70 Estimate
- 8.750 periods
- Growth Multiple
- 6.3412 x
Step by step
- 1Values used
- 2Doubling Time
- 3Doubling Time= 9.0065 periods
- 4Quantity After the Period= 6,341.181
- 5Doublings Achieved= 2.6648
- 6Rule of 70 Estimate= 8.750 periods
- 7Growth Multiple= 6.3412 x
Assumptions and limits
- The result is derived only from the 3 inputs listed above. Anything not among them is not part of the calculation.
- In particular, this calculator does not take inflation, tax or fees or charges into account.
- Figures are rounded for display to 4 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.
How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.
Frequently Asked Questions
How is Doubling Time calculated?
t_double = ln2 ÷ ln(1 + r); rule of 70: t ≈ 70 ÷ growth percentage Doubling time comes from the logarithmic form of compound growth. The rule of 70 approximates it well at low rates and drifts upward as rates rise above about 15 per cent.
Why does Doubling Time matter?
Doubling time is the most intuitive way to convey exponential growth, whether for bacteria, compound interest or data volumes.
What values do I need to enter?
This calculator takes 3 inputs: Growth rate per period, Number of periods, Initial quantity. The pre-filled defaults are a realistic starting point — replace them with figures from your own environment for a result you can act on.