Rule of 72 Calculator
Quick doubling time estimate: 72 divided by annual return. Plus exact formula, Rule of 114 and 144.
| Investment | Rate (%) | Doubling (Years) |
|---|---|---|
| Savings Account | 3.5% | 20.6 |
| Bank FD (1-3 yr) | 7% | 10.3 |
| PPF | 7.1% | 10.1 |
| NPS (mixed) | 10% | 7.2 |
| Equity MF | 12% | 6.1 |
How to Use Rule of 72 Calculator
- Choose your mode. Select “Rate → Doubling Time” if you know the return rate, or “Years → Required Rate” if you have a target number of years and want to know what rate you need.
- Enter the known value. Input the annual return percentage (e.g., 12 for equity) or the number of years you want your money to double.
- Click Calculate. The tool applies 72 divided by the rate (or years) to give the doubling time. It also shows the exact result using the natural log formula for comparison.
- Check the bonus rules. The Rule of 114 (tripling time) and Rule of 144 (quadrupling time) are displayed alongside, plus a table of common Indian investment rates with their doubling times.
Benefits of Rule of 72 Calculator
- Shows both the quick mental‑math approximation and the exact mathematical result, so you know how close the rule is for any given rate.
- Includes Rules of 114 and 144, extending the concept to tripling and quadrupling — useful for long‑term goal planning.
- The ready‑reckoner table for FD, PPF, NPS and equity saves you from looking up typical return rates.
- No finance background needed; the formula is explained simply and the calculator does the rest.
Frequently Asked Questions
Why 72 and not another number?
72 is divisible by many small integers (6, 8, 9, 12), making mental math easy. The exact divisor would be 69.3 for continuous compounding, but 72 is close enough for typical investment returns of 6‑12%.
Does the Rule of 72 work for SIPs?
No, it is designed for a one‑time lump sum. For SIPs, the concept doesn’t apply directly because each instalment has a different investment duration. Use an XIRR calculator for SIP returns.
Can I use the Rule of 72 for inflation?
Yes, to estimate how long it takes for the purchasing power of your money to halve. At 6% inflation, the value halves in approximately 72 ÷ 6 = 12 years.
Is Rule of 72 Calculator free and private?
Yes — it is 100% free, needs no sign‑up, and everything runs in your browser; your data never leaves your device.
Disclaimer: The Rule of 72 is an approximation. Use for quick mental math only.