How to use the rule of 72 doubling time calculator
Estimate how long it takes to double at a growth rate. Enter growth rate in the field above; the approximate doubling time, exact doubling time are computed instantly and plotted on the chart so you can see how the answer changes.
Formula
Variables
- r — Growth rate (%)
Worked example
With growth rate = 6 %, the calculator gives approximate doubling time ≈ 12; exact doubling time ≈ 11.89566.
Frequently asked questions
What is the formula for the rule of 72 doubling time calculation?
Approximate doubling time = 72 / r. Exact doubling time = ln(2) / ln(1+r / 100). Here r is growth rate (%).
What inputs do I need for the rule of 72 doubling time calculator?
You need growth rate in %. Each field is pre-filled with a typical example so you can see how the result responds as you edit the numbers.
How do I use this calculator?
Type values into the input fields. Results and the chart update instantly. Use Reset to restore the example values, Copy results to paste them elsewhere, or Share to copy a link that preserves your inputs.
Is the result exact?
Calculations use standard formulas and double-precision arithmetic, then display about seven significant figures. Real-world measurements carry uncertainty, so treat results as estimates unless your inputs are exact.