You can use the Rule of 72 to quickly estimate how many years it takes to double your money at a given interest rate. Albert Einstein, one of the most famous scientists of modern times, loved the Rule of 72 and referring to compound interest, is quoted as saying:
"Compound interest is the greatest mathematical discovery of all time"
If you can remember E = mc² you should be able to remember this:
72 ÷ interest rate = # of years to double your moneyRemember, this formula is an approximation not 100% accurate, but pretty close. If you’d like to calculate numbers to the nearest cent, here’s the actual compound interest formula:
Example: 72 ÷ 10 (%) = 7.2 (years)
$1,000 invested at 10% would take 7.2 years to grow to $2,000
Pn = P0 (1+r)n
Where,
Pn = Future Value
P0 = Present Value or Principal
r = interest rate (per year)
n = time (in years) a.k.a. compounding periods
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