Question 1

What is the Rule of 72 in finance?

Accepted Answer

The Rule of 72 is a finance shortcut to estimate doubling time for money under compound growth. Divide 72 by your expected annual return rate. For example, at 12% return, doubling time is about 6 years.

Question 2

What is the formula for the Rule of 72?

Accepted Answer

Rule of 72 formula: Years to double = 72 / annual return rate (in percent). If your return is 8%, estimated doubling time is 9 years (72 / 8).

Question 3

Can you show a Rule of 72 example?

Accepted Answer

If an investment earns 9% per year, Rule of 72 estimates doubling in about 8 years (72 / 9). The exact compound-interest answer is close, which makes this a useful quick check.

Question 4

Rule of 72 vs Rule of 70: when should I use each?

Accepted Answer

Use Rule of 72 for most everyday investing return assumptions. Rule of 70 or 71 can be slightly better at very low growth or inflation rates. For high precision, use the exact compound-interest formula.

Question 5

How accurate is the Rule of 72?

Accepted Answer

It is generally most accurate in normal investing ranges, and less precise at very low or very high return rates. Treat it as a fast approximation, then validate with exact calculations for important decisions.

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