The Pew Research Center developed estimates of the religious makeup of more than 200 nations and territories some years ago, which were published in the 2012 study "The Global Religious Landscape." According to this study, there are approximately 7 billion people on earth, of whom almost 3 billion are Christians and 1.6 billion are Muslims. The remaining millions belong to other religions or have no religion at all.
This makes a total of about 4,000 different religions on earth today. However, only a small fraction of those exist in every country, so the number of true religions is likely to be much lower. According to the study, there are between 300,000 and 500,000 distinct religions in existence today.
By comparison, there are only about 100,000 cars registered in the United States. This means that there are about 30 million unregistered cars in America. But most of these are not expensive luxury cars, but rather less-expensive models that fall out of use when their engines fail or they are damaged beyond repair. So the real number of unregistered cars in America may be as high as 50 million.
There are also about 70 million homes in the United States, of which approximately 10 million are apartments. This means that there are about 7 million empty apartments in America today.
By the year 2000, 161 nations adhered to one or more of the three monotheistic faiths, accounting for 86 percent of the 188 countries for which data is available and almost 3.3 billion people, or around 55 percent of the world's population.
The most common form of religion in these countries is called Christianity. It is estimated that around 795 million people, or 67 percent of the total number of Christians worldwide, live in these 161 countries.
Another 295 million people, or 27 percent of all Christians, live in the rest of the world outside of these countries. Together, they make up what is known as the Christian minority world-wide.
Finally, another 6 million Jews and other religious minorities live in these countries.
So overall, about 95 percent of the world's population is not Jewish or Christian.
The remaining 5 percent consists of Muslims, Hindus, Buddhists, and others. There are approximately 1.6 billion Muslims worldwide, making them nearly a quarter of the global population. Islam is the largest single religion in terms of both population and land area, with over half of the humans on earth being Muslim. Next is Christianity with nearly 15% of the human race being Christian. Finally, there are about 4 million Jews living in Israel and the surrounding countries.
According to a 2012 worldwide assessment of 230 nations and territories conducted by the Pew Research Center, 16% of the world's population is not associated with any religion. This includes those who say they have no religion, those who believe in a god but do not attend services, and those who identify with a religious group but may not be involved in all aspects of church life.
Of the 10 most populous countries, only India has a majority (51%) of its population that is religiously identified. The next largest minority is in China where 44% of the population identifies itself as religious.
In terms of percentage of the population that is religiously identified, Japan has the highest rate at 93%, followed by Germany at 92%. Africa has the lowest rate with an average of about 40% over the 10 most populous countries on the continent.
Even among countries that have a large proportion of their populations identified as religious, there is wide variation in how much those populations associate with specific religions. For example, while 24% of Poland's population describes itself as Catholic, only 7% of Americans do so.
The vast majority of countries in Asia and Europe are considered religious, with only Latin America and the Middle East having predominantly secular populations.
The globe has around 4,300 faiths. This is according to Adherents, a non-religious group that tracks the number and size of the world's faiths.
They estimate that there are about 150 million Christians worldwide and 100 million Muslims. There are also hundreds of thousands of Jews and Hindus.
Other estimates put the number of Christians at more than 1 billion and the number of Muslims at almost 1 billion. Either way, most people are not members of a single religion. The largest groups by far are Christianity and Islam. But among those groups, there are many subgroups.
For example, there are over 10,000 different churches within the Christian tradition. And within Islam, there are millions of different interpretations of what it means to be a Muslim.
Both numbers are growing rapidly. According to some projections, 80% of all humans will be followers of a religious group by 2100.
Why are people joining religions? Most join a church or temple where they can meet other people, make friends, and find community support. Religious leaders say that people join for social reasons, because they want to belong to something, or because they think it'll help them get into heaven.
But others join for political reasons.
Background Essay about World Religions Map
What is the total number of faiths in the world? According to most researchers, there are around 4200 active faiths in the world. Of these, about 70 percent are considered independent religions or sects.
The number of religions has increased over time. In 1900, there were about 4000-5000 religions on Earth; now there are more than 5500. The majority of these religions are independent from each other.
The most common answer when asked how many religions there are on Earth is "one". However, this question cannot be answered with any degree of certainty because it depends on what you mean by "religion". Is a religious community sufficient for counting? If so, then the answer is yes. There are several large religious communities in the world that would easily fit this definition, including Buddhism, Christianity, Hinduism, and Islam.
However, if you are asking about all organized religions, then the answer is not quite one. There have been times in history when there have been more than five hundred distinct religions across the globe at once, but such periods are rare.
Overall, it is safe to say that there are more than one religion in the world today, though exactly how many is difficult to say.