how to calculate the sum os actual month

[#1]

how to calculate the sum of actual month

[#2]

You need to provide a little more information than that if you want people on the forum to be able to help you.

[#3]

I am having tha data which consists of 2 years

and from that one I am using pivot table if i wanted to see tha actual month data that means if i select March it should show me the sum of the field in the month of March

[#4]

You will need to first connect your field to a date field using a master calendar.  Then you can use a list box for 'Month', which will automatically narrow the data to only March data when you select March.