Most of the numbers used in Revelation have the symbolic meaning that were elsewhere used in the Old Testament. Ten was a symbol of perfection or completeness, as was the number of 1,000. Seven had the sense of complete, or full. Twelve generally reminded them of the twelve tribes of Israel, and collectively of the apostles of the New Testament. There twenty-four priestly courses. The number 40 was a time of testing and proving.
The 144,000 was 12x12x1000 for the twelve tribes of Israel multiplied by the 12 apostles of the gospel of Christ (a squared number of perfection) multiplied a third time by the symbol of complete fullness, 1000.
The best understanding of God's number system is to rely upon His original use of them from the scriptures. Mostly, they are literal, but they can also be symbolic. Some discussion of numbers as used in scripture can be found here.
The Hebrews / Jews of Christ's day did not commonly believe in the use of "gematria" to study the Bible. The peoples who did assign numerical values to letters were those of the nations - the Romans (V=5, X=10, L=50, etc) and the Greeks (Epsilon = 5, Iota = 10, Nu = 50, etc.). It was the pagan nations who assigned mystical meanings to names with the use of numbers.
Excerpt from an article at MyJewishLearning.com:
"While gematria was used periodically in the Talmud and Midrash, it was not central to rabbinic literature. The rabbis occasionally employed gematria to help support biblical exegesis, but did not rely on it heavily. They were much more invested in the use of logical reasoning and argumentation to support their positions.
However, gematria is essential to, the Jewish mystical tradition. The very basis of the kabbalistic cosmological system rests on the belief that God created the universe through the power of the Hebrew letters along with their numerical values. Indeed the many names of God and their permutations in Kabbalah have numerical values that are believed to contain potent power." Source: here
The present teaching of gematria comes from Babylonian and Greek practices. Excerpt from JewishVirtualLibrary.org:
"The use of letters to signify numbers was known to the Babylonians and the Greeks. The first use of gematria occurs in an inscription of Sargon II (727–707 B.C.E.) which states that the king built the wall of Khorsabad 16,283 cubits long to correspond with the numerical value of his name. The use of gematria (τὸ ὶσόψηφον) was widespread in the literature of the Magi and among interpreters of dreams in the Hellenistic world. The *Gnostics equated the two holy names Abraxas (ʾΑβράξας) and Mithras (Μίθρας) on the basis of the equivalent numerical value of their letters (365, corresponding to the days of the solar year). Its use was apparently introduced in Israel during the time of the Second Temple, even in the Temple itself, Greek letters being used to indicate numbers (Shek. 3:2)." Source: here
The background of Revelation is of the first century A.D. It was written in code by a Jew, the apostle John, to a Jewish audience, the first century Christian converts of the seven churches of Asia. It was most likely written in AD 66-68 as indicated in the preface of the Syriac text.
The traditional date of AD 95 which the "church" fathers assigned to Revelation is out of bounds considering the text. By AD 95 the city and temple at Jerusalem had been in ruins for 25 years. But, we know that the temple was still standing when John wrote the book as he was told to measure it (Rev. 11: 1-2).
The reference to the on-going sacrificial practices at the temple by those "which say they are Jews and are not" and "that synagogue of Satan" in Rev. 2:9 and 3:9 were present tense at the time of the writing.
The "great city, which IS spiritually called Sodom and Egypt" was identified as Jerusalem "where our Lord was crucified" in the very same verse (Rev. 11:8) and shows the present tense existence at the time of the writing.
The book must be viewed in the contemporary historical time frame of the first century A.D. See more at DatingTheNewTestament.com here.
As the first century A.D. was the time of the writing of the book, the codes used in the book had to have meaning for its audience - the first century Jewish followers of Christ. The book is highly symbolic, highly metaphorical in the Eastern poetical style. But, the code the Jews knew and understood was the TaNaKh (the Torah, Nevi'im, and Ketunim) or, the Christian Old Testament scriptures.
It had to be coded because of the political strife of the times as Judea was a province under Roman rule, and the Christians were being persecuted by both the Romans and the Sanhedrin. The name of the beast had to be encoded so that the readers of the book, as well as the author of the book would not be hunted down and killed.
So, John surely used a method that was common practice of the day in Greek thinking. And, as the Jews of the day spoke and read both Aramaic and Greek the number of the beast would have been automatically calculated either way. In fact, it was just confirmation, as they already knew who was persecuting them. The Roman historians Tacitus and Seutonius nicknamed Nero "the beast".
See the post RomansinRevelation.
Rev. 13:18,
" Here is wisdom. Let him that hath understanding count the number of the beast: for it is the number of a man; and his number is Six hundred threescore and six." (KJV)
It was the number of A MAN- a man who was living at the time the book was written. The man that was the source of the persecution (tribulation) of the saints was Caesar Nero, and in Hebrew was spelled Neron Kesar. The consonants were nrwn qsr; in Hebrew "נרון קסר".
Excerpt from "Calculating the Number of the Beast" by Gary DeMar:
"So what name is behind the cryptic 666? When Nero Caesar’s name is transliterated into Hebrew, which a first-century Jew would probably have done immediately, he would have gotten Neron Kesar or simply nrwn qsr, since Hebrew has no letters to represent vowels. (The w represents a long “o” sound and the q represents the “k” sound in Hebrew.) “It has been documented by archaeological finds that a first century Hebrew spelling of Nero’s name provides us with precisely the value of 666. Jastrow’s lexicon of the Talmud contains this very spelling.”4 When we take the letters of Nero’s name and spell them in Hebrew, we get the following numeric values: n = 50, r = 200, w = 6, n = 50, q = 100, s = 60, r = 200. Put together, the sum is 666." Source: here
This numerical valuation of the name was an accommodation for the time, and did not denote a systemic practice for Biblical hermeneutics. There are many instances when the Holy Spirit used a reference that the people would hear and understand (Rev. 11:9) in their contemporary time frame. The practice of gematria was from pagan nations, and should not be the first thought for understanding the Bible.
The sound hermeneutical practice is that scripture interprets scripture, and the first use of the words from the Old Testament scriptures is carried forward. It must be understood historically, grammatically, and contextually.
The books of the New Testament were all written almost 2,000 years ago, and all were written before the destruction of Jerusalem. That makes them history for us, and they must be understood from a contemporary historical perspective of the first century A.D.
The entire article from American Vision referenced above is an excellent study. My post "The Beast of Revelation" and "It's Not The End of The World - Part V- Dating The Book of Revelation" contain further information on the subject. They are at my blog: ShreddingTheVeil.
All bold emphasis is mine.
"How are we expected to 'calculate the number'?". This question is intended to be more of a historical survey of which numerological methods were actually in use at the time - that might be applied throughout the Book of Revelation. I figure that any answers to this question might indirectly inform that one. I really, really, don't want to solicit opinions on how each number should be calculated.