IRR, like all financial functions will give you the periodic interest rate.
That's because IRR doesn't know, nor care, what period you are using. It could
be months, years, days, etc.

To convert a monthly rate to an annual rate, there are standard formulas. But I
always like to ask the question, "If you invested $100 at x% per month, how much
would you owe at the end of the year?" That will tell you what the annual rate
is. This formula is:

=fv(IRR(...),12,0,-100)

If the result is, say, $114.50, your APR is 14.5%.

The full formula to calculate the APR would be:

=FV(IRR(...),12,0,-1)-1

--
Regards,
Fred


"MJW" wrote in message
...
How does one annualize a series of monthly cash flows (usually greater 12
months)using the irr calculation ? Do you multiply the result of the
calculation by 12 (i.e. 12 months per year) or do you multiply by the number
of months in the calculation period ?