How many religions are?

Answer 1

Major Religions Chart
1. Christianity 2.1 billion
2. Islam 1.3 billion
3. Secular/Irreligious/Agnostic/Atheist 1.1 billion
4. Hinduism 900 million
5. Chinese traditional religion 394 million
6. Buddhism 376 million (see also buddhism by country)
7. Primal indigenous 300 million
8. African traditional and diasporic 100 million
9. Sikhism 23 million
10. Juche 19 million
11. Spiritism 15 million
12. Judaism 14 million
13. Bahá'í Faith 7 million
14. Jainism 4.2 million
15. Shinto 4 million
16. Cao Dai 4 million
17. Zoroastrianism 2.6 million
18. Tenrikyo 2 million
19. Neopaganism 1 million
20. Unitarian Universalism 800,000
21. Rastafari movement 600,00

Answer 2

Like the old saying goes "More than you can shake a stick at!"

Some religions have one (1) follower others claim a third of the human population. In some jurisdictions a "real " religion (for tax purposes) has to be registered. Other folks feel that since they've founded their religion on direct divine instructions no gov't agency should need to be involved. Then there are sects of existing religions who may be claimed or disavowed by the parent group. There is no truly accurate answer.

The appended link lists 1000 Religions. Not truly an exhaustive list, it has Jedi, but misses the Church of the SubGenius and Pastafariansm.