How to display number of entries for a tag and not display if no entries?
Something like this should work:

{% set tags = craft.tags.limit(null).relatedTo(craft.entries.limit(null)).order('title') %}

{% for tag in tags %}
    &lt;a href="/tags/{{ tag.slug }}"&gt;{{ tag.title }} (craft.entries.relatedTo(tag).total())&lt;/a&gt;
{% endfor %}


Note that if you have a significant amount of tags, the above could be a costly affair, performance wise – consider alternative approaches.