Rule of 72 Calculator — Years to Double
Estimate years to double with the Rule of 72: years ≈ 72 ÷ annual rate%. Sample: 6% → about 12 years. A quick teaching approximation — not investment advice Calculate approximate doubling years with the Rule of 72 formula; example 6% → 12 years.
How it works
Enter an annual percentage rate. The classic Rule of 72 divides 72 by that rate to sketch doubling time.
Formula
Years ≈ 72 / r_percent. Notes:
- Works best for moderate rates; very high/low rates are less accurate.
- Assumes annual compounding style intuition, not a full schedule.
- Compare with compound-interest / CAGR tools for precise math.
Example
Example: rate 6% → 72/6 = 12 years.
When to use it
- Classroom doubling-time intuition.
- Quick sketch before precise FV math.
- Pair with CAGR and compound interest.
Frequently asked questions
Sample?
6% → 12 years.
Exact?
No — a teaching approximation.
Why 72?
A convenient number near the natural-log doubling math.
Advice?
Educational only.
Important notice
Educational rule of 72 only — not financial, tax, or investment advice.
References: Investopedia and standard textbook formulas.
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Questions or feedback
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