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Doubling Time Calculator — result sheet
Find how long a quantity takes to double under a constant percentage growth rate, or find the periodic rate needed to double in a chosen time.
Inputs used
Results
Visual chart
Breakdown
Calculation steps
Returned data table
Formula and methodology
Formula: For discrete growth r, t₂ = ln(2)/ln(1+r); reversing gives r = 2^(1/t₂)−1. Under continuous growth A=A₀e^(kt), t₂=ln(2)/k.
Doubling time is a property of the growth rate, not the starting amount. This two-way calculator makes that independence explicit, while also showing the amount after one doubling and the equivalent continuous rate for comparison.
This result follows the calculator's declared inputs, precision, validation boundaries, and model limits.
Input contract
- Calculate — 2 choices
- Periodic growth rate — % per period; minimum 1.0E-6; maximum 1000000
- Doubling time — periods; minimum 1.0E-6; maximum 1000000
- Initial amount — units; minimum 1.0E-6; maximum 1000000000000
Worked example
| Input | Value |
|---|---|
| Calculate | timeFromRate |
| Periodic growth rate | 15 |
| Doubling time | 5 |
| Initial amount | 1000 |
At 15% growth per period, the doubling time is about 4.960 periods; 1,000 becomes 2,000 after one doubling.
Assumptions and limits
- The rate is constant and positive for the selected periods; changing rates or saturation requires a different model.
- The periodic rate is compounded once per stated period, while the continuous rate is an equivalent exponential parameter.
- The initial amount is used only to show the doubled amount; it does not change the calculated time.
Calculator note
Source and methodology
Use the official WorldCalculate methodology policy for the source, formula, precision, and boundary standards behind this calculator.
Planning estimate, not financial, medical, legal, or professional advice. © WorldCalculate — reuse with attribution. Built and curated by Hassan ALRowaie.
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