Free Rule of 72 Calculator - Calculates how long it would take money to double (doubling time) using the rule of 72 interest approximation as well as showing the mathematical proof of the Rule of 72.

This calculator has 1 input.

This calculator has 1 input.

Doubling Money Time (t) = 0.72/i

(1 + i)^{t} = 2

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(1 + i)

For more math formulas, check out our Formula Dossier

- approximation
- anything that is intentionally similar but not exactly equal to something else.
- compound interest
- the interest you earn on principal and interest

A = (1 + r/n)^{nt} - interest rate
- the proportion of a loan that is charged as interest to the borrower or proportion of principal credit given to a depositor
- logarithm
- the exponent or power to which a base must be raised to yield a given number
- rule of 72
- a simplified formula that calculates how long it will take for an investment to double in value, based on its rate of return.

t ~ 72/i - yield
- How much an investment returns in terms of interest rate

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