I'll derive the formula for you, and give an example in which your deposit is compounded monthly.

D = deposit

y = number of years deposited

t = number of times compounded annually

A = 6.5 %

r = A / t

ty = number of periods compounded

D ( 1 + r )

(1 + r )

ln ((1 + r )

ty ln(1 + r ) = ln (2 )

ty = [ln(2)] / [ln (1 + r)]

ty = [ ln(2) ] / [ ln ( 1 +( 0.065/12) )]

ty = 128.31

It will take 128.31 months for you deposit to double if compounded monthly.

After 129 months you will more than double your deposit.

If your deposit is compounded differently ( daily, quarterly or annually) make the necessary

substitutions to get the results you're looking for.

D = deposit

y = number of years deposited

t = number of times compounded annually

A = 6.5 %

r = A / t

ty = number of periods compounded

D ( 1 + r )

^{ty}= 2D(1 + r )

^{ty}= 2ln ((1 + r )

^{ty}) = ln (2)ty ln(1 + r ) = ln (2 )

ty = [ln(2)] / [ln (1 + r)]

ty = [ ln(2) ] / [ ln ( 1 +( 0.065/12) )]

ty = 128.31

It will take 128.31 months for you deposit to double if compounded monthly.

After 129 months you will more than double your deposit.

If your deposit is compounded differently ( daily, quarterly or annually) make the necessary

substitutions to get the results you're looking for.