Rule of 70

The rule of 70 is a method for estimating an investment's doubling time.

The investment doubling time is proportional to the reciprocal of the interest rate.

Formula

QuantityVariable[Subscript["T", "d"], "Time"] == Quantity[4900, "Percent"*"Years"]/QuantityVariable["i", "Unitless"]

symbol	description	physical quantity
T_d	investment doubling time	"Time"
i	interest rate	"Unitless"

Get the resource:

In[1]:=

Out[1]=

Get the formula:

In[2]:=

Out[2]=

Use some values:

In[3]:=

$FormulaData[ResourceObject["Rule of 70"], {QuantityVariable[ \!$\*SubscriptBox[\("T"$, $"d"$]\),"Time"] -> Quantity[2, "Years"]}]$

Out[3]=