Show total number of posts in category on the category page

I’m wanting to display the total number of posts within the category on the category template page in the title, so it reads something like:

There are xx number of posts i the category.

I tried
<?php echo $wp_query->post_count ?>
but that just gives me total number displayed on the page, not the entire category. How can I get just the number of posts in the current category?

I also need to do the same for my tags.