In Excel, how do I calculate the number of periods to apply an in.

[Guest]

I have captial X and rate of interest R. I want to know how many periods it
will take to reach amount Y, given that interest applied to capital becomes
compounded each month.
I looked at NPER, but NPER requires a payment each month, and if I specify 0
then an error is returned.
Is there another way?

 

[Jack Schitt]

I don't know if there is a dedicated Excel function for you (others will
pile in), but if I recall my school maths you can get to it by

=(LN(P)-LN(X))/(1+LN(R))

This assumes that R is the monthly interest rate.

 

[sulprobil]

You can use NPER():

=NPER(10%,0,-100,121)

would result in 2 because if you invest $100 over 2
periods with interest rate 10% and 0 further periodical
payments you would receive $200.

HTH,
sulprobil

 

[Jack Schitt]

Sorry, for LN(P) read LN(Y)

I don't know if there is a dedicated Excel function for you (others will
pile in), but if I recall my school maths you can get to it by

=(LN(P)-LN(X))/(1+LN(R))

This assumes that R is the monthly interest rate.

specify