The 'Rule of 72' is a simplified way to determine how long an investment will take to double, given a fixed annual rate of interest. By dividing 72 by the annual rate of return, investors can get a rough estimate of how many years it will take for the initial investment to duplicate itself.

For example, the rule of 72 states that $1 invested at 10% would take 7.2 years ((72/10) = 7.2) to turn into $2. In reality, a 10% investment will take 7.3 years to double ((1.10^7.3 = 2).

When dealing with low rates of return, the Rule of 72 is fairly accurate. This chart compares the numbers given by the rule of 72 and the actual number of years it takes an investment to double.

Rate of Return Rule of 72 Actual # of Years Difference (#) of Years
2% 36.0 35 1.0
3% 24.0 23.45 0.6
5% 14.4 14.21 0.2
7% 10.3 10.24 0.0
9% 8.0 8.04 0.0
12% 6.0 6.12 0.1
25% 2.9 3.11 0.2
50% 1.4 1.71 0.3
72% 1.0 1.28 0.3
100% 0.7 1 0.3

Notice that, although it gives a quick rough estimate, the rule of 72 gets less precise as rates of return become higher. Therefore, when dealing with higher rates, it's best to calculate the precise number of years algebraically by means of the future value formula.

(To learn more, see Understanding the Time Value of Money.)

  1. How do I use the rule of 72 to estimate compounding periods?

    The rule of 72 is best used to estimate compounding periods that are factors of two (2, 4, 12, 200 and so on). This is because ... Read Full Answer >>
  2. How do I calculate the rule of 72 using Matlab?

    In finance, the rule of 72 is a useful shortcut to assess how long it takes an investment to double given its annual growth ... Read Full Answer >>
  3. How do I use the rule of 72 to calculate continuous compounding?

    The rule of 72 is a mathematical shortcut used to predict when a population, investment or other growing category will double ... Read Full Answer >>
  4. How do I adjust the rule of 72 for higher accuracy?

    The rule of 72 refers to a time value of money formula that investors use to calculate how quickly an investment will double ... Read Full Answer >>
  5. What is a stock split? Why do stocks split?

    All publicly-traded companies have a set number of shares that are outstanding on the stock market. A stock split is a decision ... Read Full Answer >>
  6. How do I place an order to buy or sell shares?

    It is easy to get started buying and selling stocks, especially with the advancements in online trading since the turn of ... Read Full Answer >>
Related Articles
  1. Active Trading

    10 Steps To Building A Winning Trading Plan

    It's impossible to avoid disaster without trading rules - make sure you know how to devise them for yourself.
  2. Mutual Funds & ETFs

    Best 3 Vanguard Funds that Track the Top 500 Companies

    Discover the three Vanguard funds tracking the S&P 500 Index, and learn about the characteristics and historical statistics of these funds.
  3. Forex Education

    Time Value Of Money: Determining Your Future Worth

    Determining monthly contributions to college funds, retirement plans or savings is easy with this calculation.
  4. Investing Basics

    A Simplified Approach To Calculating Volatility

    Volatility is sometimes greater than anticipated, but the way it’s measured can compound the problems that occur when it’s unexpected.
  5. Investing Basics

    Should You Trade Forex Or Stocks?

    Deciding whether to trade stocks, foreign exchange or futures contracts typically comes down to risk tolerance, account size and convenience.
  6. Investing Basics

    What's a Benchmark?

    A benchmark is a standard investors choose to gauge the performance of their portfolios.
  7. Investing Basics

    How MasterCard Pulled Off a Buyback

    Stock buyback refers to publicly traded companies buying back their shares from shareholders. Why would they do that?
  8. Entrepreneurship

    How To Raise Seed Capital and Grow Your Startup

    To get a business off the ground, entrepreneurs need a clear understanding of how to strategically position themselves for VC firms and angel investors.
  9. Trading Strategies

    The Elements of a Perfect Momentum Trade

    Five technical elements build profits in high-risk momentum trading strategies.
  10. Investing Basics

    6 Dangerous Moves For First-Time Investors

    Anyone with an Internet connection and a bank account can trade stocks. But it’s important to avoid mistakes that are common among first-time investors.
  1. Markdown

    The difference between the highest current bid price among dealers ...
  2. Catalyst

    A catalyst in equity markets is a revelation or event that propels ...
  3. Investing

    The act of committing money or capital to an endeavor with the ...
  4. Bid Wanted

    An announcement by an investor who holds a security that he or ...
  5. Hindsight Bias

    A psychological phenomenon in which past events seem to be more ...
  6. Paper Trade

    Using simulated trading to practice buying and selling securities ...

You May Also Like

Hot Definitions
  1. Take A Bath

    A slang term referring to the situation of an investor who has experienced a large loss from an investment or speculative ...
  2. Black Friday

    1. A day of stock market catastrophe. Originally, September 24, 1869, was deemed Black Friday. The crash was sparked by gold ...
  3. Turkey

    Slang for an investment that yields disappointing results or turns out worse than expected. Failed business deals, securities ...
  4. Barefoot Pilgrim

    A slang term for an unsophisticated investor who loses all of his or her wealth by trading equities in the stock market. ...
  5. Quick Ratio

    The quick ratio is an indicator of a company’s short-term liquidity. The quick ratio measures a company’s ability to meet ...
  6. Black Tuesday

    October 29, 1929, when the DJIA fell 12% - one of the largest one-day drops in stock market history. More than 16 million ...
Trading Center