The answer to that question can vary, depending on the definition of "saint."
The word “saint” comes from the Latin word sanctus, meaning “holy.” During the first several centuries of the Church, this title was freely given to all those, primarily martyrs, who were publicly known for their holiness.
It wasn’t until 1588 that the Vatican’s Congregation for Saints’ Causes was officially created to help regulate this title and be more selective regarding the process of formal canonization.
Few people have had the time to sort through even these several centuries of saints and come up with a tally of officially canonized saints.
In general the range of answers to this question is between 1,000 and 8,000 saints. However, this may not include the vast number of saints that have been canonized in the past few decades.
For example, St. John Paul II canonized 482 saints, Pope Benedict XVI canonized 45 saints and Pope Francis has alone canonized 893 saints. These numbers are often high on account of “mass” canonizations, such as the canonization of 800 Italian martyrs by Pope Francis in 2013.
On the other hand, most people agree that the number of “saints” is impossible to calculate, as the term can also refer to all those people currently in Heaven.
Some people claim there have been at least 100 billion births since the beginning of human existence. How many of those people are in Heaven is a matter of speculation, and none of us will definitively know that until the end of our own lives on earth.
What does matter is that everyone is called to holiness and should strive to become a saint. Holiness is attainable to anyone who desires a close relationship with Jesus and can be achieved in any profession or vocation on earth.
Can a sinner become a saint?