Hungary's monthly CPI growth rate has been as follows for the past 3 months:

Dec 18 - $2.8\%$

Jan 19 - $3.2\%$

Feb 19 - $3.5\%$

I am wondering how you'd calculate the annualized growth rate $r$ from the past 3 months, as inflation there is obviously accelerating and I would like to know the extent to which it has accelerated in the past 3 months on an annualized basis.

I was thinking that I could use the formula:

$$r = \left(1 + \frac{\text{End Value}}{\text{Start Value}}\right)^{12/3}-1$$

But I don't think that applies here?