When to use this calculator
Unlike the Rule of 72 approximation, this solves the exponential relationship directly for any supported positive rate.
Explore the algebra & number calculators for other questions in this topic. For a related calculation, use the Exponent Calculator: Raise a positive base to a chosen exponent.
PUTTING IT INTO PRACTICE
Doubling Time: a worked example
The values below are an illustrative example, not a recommendation. Replace them with measurements or assumptions that match your question.
| Input | Example value |
|---|---|
| Growth per period (%) | 100 |
| Result | 1 periods |
- Check the input labels and enter the example values above.
- Apply the relationship: Doubling time = ln(2) ÷ ln(1 + growth/100).
- The result is 1 periods, rounded for display.
How to interpret your result
Uses a fixed effective rate per period, without deposits, withdrawals or changing growth.
Identify whether the question asks for one term, a total or a count of possible selections. Sequences use a fixed difference or ratio. In counting problems, order and replacement determine the correct model.
Frequently asked questions
Do combinations and permutations count the same thing?
No. Combinations ignore the order of selection; permutations count different orders separately.
When is the doubling time calculator useful?
Unlike the Rule of 72 approximation, this solves the exponential relationship directly for any supported positive rate.
How do I use the doubling time calculator?
Enter growth per period (%). The result updates automatically. Use the units shown beside each input; the example values illustrate the method.
Which formula does this calculator use?
Doubling time = ln(2) ÷ ln(1 + growth/100).
What should I check before using the result?
Uses a fixed effective rate per period, without deposits, withdrawals or changing growth.
How are results rounded?
Scalar numbers display up to six decimal places, with scientific notation for very large or small values. Text, fraction, date and schedule outputs use the format described on the tool. Intermediate calculations use JavaScript floating-point arithmetic. Keep sensible precision for your measurements.
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