What percentage of the Bible consists of the Old Testament?

I am really lousy at math but if you figure Old Testament has 39 books (this is generally) and New testament has 27.
You add it up to 66. Then do division for percentage which I believe makes it 40% compared to 60% of Old Testament (yes I rounded it( But the Old Testament consists of generations of myths, legends, prose, poetry, songs and history of the Israelites. From when the world began up to but not including the herald of the one crying in the desert John the Baptist.
It is said in the New Testament that not all what Jesus did and said was written down.His public life was only 3 years.

In a Catholic Bible, which has all 73 books (as opposed to the Protestants' 66), 46 of them are from the Old Testament, or 845 pages out of 1065 total. I did the math on a calculator and that equated to 79.34% of the entire Bible.

https://en.m.wikipedia.org/wiki/Catholic_Bible

According to good old Wikipedia at the above link, "the Catholic Bible" contains 73 books.

However, when using the links within the link above, "the Catholic Bible" is used by "the Catholic Church." That link is about the Roman Catholic church. A mention, and link, is made for "Eastern Catholic churches." The link for "the Eastern Catholic churches" mentions all of those churches believe the pope in Rome, currently Pope Francis, heads the church.

This is an example of why Wikipedia is a poor source. Not every faith with Catholic in its name believes the pope is the leader. My source? Paternal grandparents, father, and years of attending mass in one of those other Catholic churches.

As for how many pages comprise the New Testament and the Old Testament, it depends on the printed edition of the bible in question. Larger pages mean less pages. Small fonts mean less pages.

The only way to know how many pages of the Old Testament are what percentage of a bible is figure it out with the bible you have.

73%

Number of letters in the King James Bible: 3,116,480
Number of letters in the Old Testament: 2,278,100

percentage of total is about 73%

https://wordcounter.net/blog/2015/12/08/10975_how-many-words-bible.html

"The Christian Old Testament features more than 24 books of the original Hebrew Bible, and deliberately in a divergent order.[11] Moreover, there are a number of different versions of the Christian Bible, with different selections of books, as well as different ordering and naming of books, or incorporation of additional material into the books.

Christian Bibles range from the sixty-six books of the Protestant canon to the eighty-one books of the Ethiopian Orthodox Church canon. The first part of all Christian Bibles is the Old Testament, which contains, at minimum, the twenty-four books of the Hebrew Bible divided into thirty-nine books and ordered differently from the Hebrew Bible. The Catholic Church and Eastern Christian churches also hold certain books and passages that are excluded from the Hebrew Bible to be part of the Old Testament canon.

The second part of the Christian Bible is the New Testament, containing twenty-seven books originally written in Koine Greek, which discuss the teachings and person of Jesus, as well as events in first-century Christianity. The New Testament is divided into the four Canonical gospels, the Acts of the Apostles, twenty-one Epistles or didactic letters, and the Book of Revelation."

https://en.wikipedia.org/wiki/Bible

To calculate the answer based on words depends on the version. Of course, any other translation would differ slightly. Bibles in other languages (such as the Vulgate, in Latin) similarly aren't exactly the same. And then there is the Douay-Rheims translation, commonly (albeit inaccurately) referred to as the Catholic Bible, which includes a number of chapters (all in the Old Testament) which are not included in the Protestant canon, so the Old Testament is correspondingly a larger percentage of that Bible.

http://www.drbo.org/
http://www.latinvulgate.com/

With all those reasons why a precise answer is not possible, the answer will generally be between 70% and 80%.

The question, "What percentage of..." something is problematic, on top of all the versions that can be compared issue. No one has given a % by weight value which is generally a sought after comparison. The number of letters and words used might be erroneous because the total number of character spaces isn't counted, only those with a character. A volume with two thousand spaces and a thousand characters (50% of the count) compared to a volume with two thousand spaces and fifteen hundred characters (75% of the possible count) as an example. Do you compare the total spaces or just the ones used for letters? In this example the characters are equal but the usage of spaces is 50% greater within the same volume. Books are a problem measure because one book may contain a thousand words while another group of books may only have 100 words each. Then there's the meaning of the written word. The Old Testament may be difficult to comprehend but brief while the New Testament is easy to comprehend but vastly longer in total words. To arrive at a fair value would require tearing the two parts of the bible apart and weighing each but that would be sacrilegious.