Short answer. Gematria (גימטריא) is the practice of reading a Hebrew word by the sum of the numerical values its letters carry, so that words or phrases with the same total are taken to illuminate one another. It appears in rabbinic literature as a homiletic and mnemonic device, becomes a generative technique in Kabbalah (most radically in Abraham Abulafia's ecstatic system) and has a Greek counterpart, isopsephy, which is what stands behind the number of the beast in Revelation. Within the tradition it functions as an asmakhta, a supporting hint attached to a conclusion reached on other grounds. Treated as a method of proof, it will confirm anything you bring to it, and this page explains precisely why.
How the values work
Hebrew has no separate numerals; the letters do the work. Alef through tet run 1 to 9, yod through tzadi run 10 to 90 in tens, and qof through tav run 100 to 400 in hundreds. The five final forms are sometimes extended to 500-900, though that is a later convention and not universally used. Letters serving as numerals is attested in Jewish material from the Hasmonean period onward (on coins, and later in manuscript pagination) so the underlying arithmetic is ordinary practice long before anyone builds an interpretive method on it.
A few totals are so well established that they function as vocabulary. YHWH sums to 26. Chai (חי, "life") is 18, which is why charitable gifts are so often multiples of eighteen. Echad (אחד, "one") and ahavah (אהבה, "love") both total 13, and their sum, 26, returns the divine Name, an elegance the tradition is fond of and a fair illustration of what the practice is actually for.
Where the word comes from: genuinely unsettled
The term is a Greek loanword into rabbinic Hebrew, and which Greek word is disputed. The usual derivation is from geōmetria, widened from measuring land to calculation generally. A serious alternative derives it from grammateia, letter-reckoning, which fits the actual practice more closely. Standard reference treatments note the uncertainty rather than resolving it (Scholem, Kabbalah, 1974, entry on gematria), and this page reports it as open. What is not in doubt is that the vocabulary is Greek, which places the technique in a Hellenistic environment where number-and-letter play was widespread.
The rabbinic use: a hint, not an argument
Gematria appears in the classical rabbinic corpus, though less often than popular accounts imply. It is listed among the hermeneutic rules in the baraita of the Thirty-Two Middot attributed to Rabbi Eliezer ben Yose ha-Gelili, an attribution scholars generally treat as later than the name claims, so its early dating should be held loosely.
The stock example is Genesis 14:14, where Abraham arms three hundred and eighteen retainers; the Talmud reports the reading that the number stands for Eliezer, Abraham's servant, whose name sums to 318 (b. Nedarim 32a). Notice what the reading does and does not do. It does not establish that only one man went. It attaches a memorable observation to a text and draws out a point about Eliezer's worth. That is the characteristic function: asmakhta, a support hung on a verse, not a derivation from it.
Isopsephy, 666, and the limits of the method
Greek letters carry numerical values on the same principle, and the Greek practice is called isopsephy. It is what Revelation 13:18 is doing when it invites the reader to "calculate the number of the beast," giving 666.
The reading that commands the widest scholarly support is Nero Caesar written in Hebrew letters (נרון קסר), which totals 666. The strongest evidence for it is textual rather than arithmetical: an early variant reading gives 616, and the Latin form Nero Caesar without the final nun totals exactly 616, so the variant is explained by the same identification (David Aune, Revelation, Word Biblical Commentary, 1998). That is a genuinely strong argument, and it also demonstrates the method's weakness with unusual clarity. Across two languages, with spelling latitude, a great many names reach 666. What distinguishes the Nero reading is not that the sum works (many sums work) but that an independent piece of manuscript evidence lines up with it. Corroboration is doing the work; the number alone never could.
Kabbalistic gematria: from reading to technique
In Kabbalah the practice changes character. The Zohar uses gematria, but sparingly relative to its reputation; its dominant modes are narrative and symbolic. The decisive turn is Abraham Abulafia's, in thirteenth-century ecstatic Kabbalah, where gematria joins tzeruf (permutation of letters) and notarikon (reading words as acronyms) as part of a practice rather than an exegesis, a discipline of combination meant to loosen ordinary cognition and produce a prophetic state (Moshe Idel, The Mystical Experience in Abraham Abulafia, 1988, and Language, Torah, and Hermeneutics in Abraham Abulafia, 1989).
The theological premise underneath is what makes this more than wordplay. If the Torah is not merely a text about God but is woven of the divine Name, then its letters are the fabric of reality and recombining them is operating on something real. Grant the premise and the technique follows; the technique never establishes the premise.
Why gematria proves nothing on its own
This is the section a reader deserves, and it is not an attack on the tradition, the tradition itself largely agrees. The problem is degrees of freedom. Standard gematria (mispar hechrachi) is only one method among many: mispar katan reduces values to a single digit; mispar gadol extends the finals to 500-900; at-bash substitutes letters by reversing the alphabet; mispar siduri numbers letters 1 to 22 by position; and a widespread convention permits adding one to a total for the word itself (kolel).
Each variant is legitimate within the tradition. Together they mean that for almost any pair of words, some admissible method makes them match. A procedure that cannot fail cannot confirm, the correspondences that survive are the ones that were already meaningful, and the arithmetic decorated them rather than discovering them.
So the honest verdict has two halves, and both are needed. Gematria is a real, well-attested and sometimes beautiful feature of Jewish interpretation, and it is not evidence. Sources presenting a numerical coincidence as proof of a hidden message (in scripture, in a name, in a date) are using a device the tradition understood as a hint, in a role the tradition did not give it.
Common questions
Is gematria in the Bible?
Not as a stated method. Hebrew letters carry numerical values, and the technique is applied to biblical verses from the rabbinic period onward, but the Hebrew Bible never sets out gematria as a way of reading. The clearest in-text instance of the underlying practice in scripture is Greek rather than Hebrew: Revelation 13:18 asks the reader to calculate the number of the beast, which is isopsephy.
Does gematria prove anything?
No, and the tradition broadly agrees. Within rabbinic interpretation gematria functions as asmakhta, a supporting hint attached to a conclusion reached on other grounds. Because several legitimate methods exist (mispar katan, mispar gadol, at-bash, mispar siduri, and the kolel convention of adding one), almost any two words can be made to match by some admissible route, and a procedure that cannot fail cannot confirm.
What is 666 in gematria?
Revelation 13:18 gives 666 as the number of the beast, using the Greek practice of isopsephy. The best-supported identification is Nero Caesar written in Hebrew letters, which totals 666. Its strength is not the sum but the corroboration: an early variant reading gives 616, and the Latin form without the final nun totals exactly 616, so one identification explains both numbers.
What are the different methods of gematria?
The standard method (mispar hechrachi) sums the ordinary values. Mispar katan reduces to a single digit; mispar gadol gives the five final letters values of 500-900; mispar siduri numbers the letters 1 to 22 by position; at-bash substitutes each letter for its counterpart from the other end of the alphabet. The kolel convention allows adding one for the word itself. All are traditional, which is exactly why the technique is so permissive.
What is the difference between gematria, notarikon and tzeruf?
Gematria reads words by numerical value. Notarikon treats a word as an acronym, expanding each letter into a word of its own. Tzeruf permutes letters to generate new combinations. Abraham Abulafia's ecstatic Kabbalah used all three together, not to interpret a text but as a practice meant to unsettle ordinary cognition and induce a prophetic state.
This page treats gematria as what the tradition treated it as (a hint hung on a conclusion, not a proof of one) sets out the methods that make it so permissive, reports the etymology as unsettled, and shows with the 666 case why corroboration, never the sum by itself, is what carries an identification.
Sources
Gershom Scholem, Kabbalah (1974), entry on gematria; Moshe Idel, The Mystical Experience in Abraham Abulafia (1988) and Language, Torah, and Hermeneutics in Abraham Abulafia (1989); A. P. Hayman, Sefer Yesira: Edition, Translation and Text-Critical Commentary (2004); David E. Aune, Revelation, Word Biblical Commentary (1998), on 13:18 and the 616 variant; b. Nedarim 32a on Genesis 14:14; the baraita of the Thirty-Two Middot attributed to Eliezer ben Yose ha-Gelili.