Investment Learning Tool

Rule of 72 Calculator

Estimate how long it may take an investment to double—or calculate the approximate annual return required to double your money within a chosen timeframe. Then compare the shortcut with precise compound growth.

Choose Your Calculation

Estimate the time required to double your investment or calculate the approximate return needed to reach a doubling goal.

Starting investment

Used to illustrate the Rule of 72 and precise compound growth.

Expected annual return

Enter an estimated annual rate of return.

Target doubling period

years

Enter the number of years in which you want the investment to approximately double.

Inflation assumption

Used to illustrate how quickly prices and the cost of living may approximately double.

Your Rule of 72 estimate

Doubling Snapshot

Educational estimate

Approximate time to double

9 years

At an estimated annual return of 8.0%.

Starting amount

$50,000

Approximate doubled value

$100,000

Precise doubling time

9.0 years

Inflation doubling time

28.8 years

Illustrative doubling timeline Approximately 9 years

Today $50,000

Year 9 $100,000

Planning insight:The Rule of 72 provides a convenient estimate. The precise result depends on compound growth and may differ slightly.

Visual Explanation of Compound Growth

The Rule of 72 is a shortcut. This section uses the compound-growth formula to show the investment’s estimated value over time.

Compound-Growth Formula

How the Investment Grows

FV = PV(1 + r)ⁿ

Current illustration:
FV = $50,000 × (1 + 0.08)⁹ ≈ $99,950

FV
Future value

PV
Starting investment

r
Annual return

n
Number of years

The Rule of 72 estimates 9 years. The precise compound-growth calculation estimates approximately 9.0 years.

Live Growth Graph

Projected Investment Value

8.0% annual return

Precise compound growth Approximate doubling point

How Different Returns Affect Doubling Time

Even relatively small differences in long-term return assumptions can materially change how quickly an investment may double.

Annual return	Rule of 72 estimate	Precise compound estimate
3%	24 years	23.4 years
4%	18 years	17.7 years
5%	14.4 years	14.2 years
6%	12 years	11.9 years
8%	9 years	9.0 years
10%	7.2 years	7.3 years
12%	6 years	6.1 years

Want to Turn a Simple Estimate Into a Financial Strategy?

A personalized investment review can help connect return expectations, inflation, risk, account selection, tax efficiency, contributions, and long-term financial goals.

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The Rule of 72 is a simplified educational estimate and is most useful for relatively moderate rates of return. The compound-growth illustration assumes a constant annual return and no additional deposits or withdrawals. Neither calculation accounts for fees, taxes, market volatility, or changing rates of return. Results are for general illustrative purposes only and do not constitute investment, tax, legal, or accounting advice.

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