What is the Rule of 72?
The Rule of 72 is a quick way to estimate how long money takes to double at a given yearly rate: divide 72 by the rate.
This calculator shows the rule-of-thumb answer, the exact answer using compound growth, and the time to triple and quadruple your money.
How it helps you
- Get a feel for compounding without complex maths.
- See how a small difference in return changes the doubling time.
- Understand inflation: at 6% inflation, prices roughly double every 12 years.
How it is calculated
Years to double ≈ 72 ÷ r (exact: ln 2 ÷ ln(1 + r ÷ 100))
- r
- Yearly rate of return or inflation, in %
- 114 ÷ r
- Approximate years to triple
- 144 ÷ r
- Approximate years to quadruple
Your money grows at 12% a year.
- 1Rule of 72: 72 ÷ 12 = 6 years
- 2Exact: ln 2 ÷ ln 1.12 ≈ 6.12 years
₹1,00,000 becomes about ₹2,00,000 in roughly 6 years.
How to use the Rule of 72
- 1Enter an amount and a yearly rate.
- 2Read the doubling, tripling and quadrupling times.
- 3Use the chart to see the growth over time.
Frequently asked questions
How accurate is the Rule of 72?
It is most accurate for rates between about 6% and 10%. At very low or very high rates the exact figure shown alongside is more reliable.
Can I use it for inflation?
Yes. Divide 72 by the inflation rate to see how quickly prices double, or how quickly the value of money halves.
Why 72?
72 is close to the exact value (about 69.3) adjusted for typical rates, and it divides easily by many numbers like 6, 8, 9 and 12.