find the number of post while using custom query

Hello
I am using a custom query to return post list .I am trying to find the total number of post returned from the query, I found a property
found_posts for the work, but it is giving 0 always even though the query is showing post.I found it is an issue with php or to say its a bug.
The code which i have used is
echo $wp_query->found_posts;

Is there any other way to find the total number of post returned by a query i am using wp_query($args)

Thanks in advance