Online Return On Investment Calculator

Online Rule 72 Calculator Use the Online Rule of 72 Calculator to estimate how long it will take to double an investment at a given interest rate. Divide 72 by the interest rate to see how long it will take to double your money on an investment. Alternatively you can calculate what interest rate you need to double your investment within a certain time period. For example if you wanted to double an investment in 5 years, divide 72 by 5 to learn that you'll need to earn 14.4% interest annually on your investment for 5 years: 14.4 × 5 = 72. The Rule of 72 is a simplified version of the more involved compound interest calculation. It is a useful rule of thumb for estimating the doubling of an investment. This calculator provides both the Rule of 72 estimate as well as the precise answer resulting from the formal compound interest calculation. Rule of 72 Formula The Rule of 72 is a simple way to estimate a compound interest calculation for doubling an investment. The formula is interest rate multiplied by the number of time periods = 72: R * t = 72 where R = interest rate per period as a percentage t = number of periods Commonly, periods are years so R is the interest rate per year and t is the number of years. You can calculate the number of years to double your investment at some known interest rate by solving for t: t = 72 ÷ R. You can also calculate the interest rate required to double your money within a known time frame by solving for R: R = 72 ÷ t. Example Calculations in Years If you invest a sum of money at 6% interest per year, how long will it take you to double your investment? t=72/R = 72/6 = 12 years What interest rate do you need to double your money in 10 years? R = 72/t = 72/10 = 7.2% Example Calculation in Months If you invest a sum of money at 0.5% interest per month, how long will it take you to double your investment? t=72/R = 72/0.5 = 144 months (since R is a monthly rate the answer is in months rather than years) 144 months = 144 months / 12 months per years = 12 years