Chaldean vs Pythagorean: which letter table, and why it matters

The two canonical letter tables side by side, where they diverge, why Chaldean has no 9, and how to decide which to trust.

29 July 2026 · 7 min read

If you have ever had two numerologists give you different numbers, this is usually why. Name-derived numbers depend entirely on which value each letter is assigned, and there is no single agreed table. The two with the strongest published pedigree are Pythagorean and Chaldean, and they disagree about most of the alphabet.

The Pythagorean table

Also called Modern or Western, and by far the most common in English-language numerology. It is a positional scheme: A is 1, B is 2, on to I at 9, then J restarts at 1. Every letter therefore maps to its position in the alphabet, modulo nine. It is trivially easy to reproduce by hand, which is a large part of why it dominates.

Its provenance is the work of Juno Jordan and, later, Hans Decoz, whose books are where most current practice descends from. Note that the attribution to Pythagoras himself is decorative — there is no evidence the historical Pythagoras used anything resembling this table.

The Chaldean table

Associated with Cheiro — the pen name of Count Louis Hamon — and with Sepharial, and much more widely used in India than in the West. It is not positional. Letters are grouped by what the tradition holds to be their sound-value, so A, I, J, Q and Y all take 1, while B, K and R take 2. There is no way to derive it; you have to look it up.

The striking feature is that no letter is assigned 9. In this tradition 9 is treated as sacred and withheld from the alphabet. A Chaldean name total can still reduce to 9 — the sum of other values often does — but no individual letter contributes it.

Where they actually diverge

Take the letter S. Pythagorean gives it 1; Chaldean gives it 3. R is 9 in Pythagorean and 2 in Chaldean — the single largest gap in the two tables. For a name of ordinary length these differences do not cancel out, and it is entirely normal for the same name to produce an Expression of 9 under one table and 6 under the other.

This has a practical consequence that is worth being blunt about: if a site gives you a name number without telling you which table it used, the number is not interpretable. You cannot compare it against anything, and you cannot reproduce it.

The Y problem

Pythagorean treats Y contextually — a vowel when it carries the vowel sound of its syllable, a consonant when it glides onto a following vowel. So the Y in Lynn is a vowel and the Y in Yolanda is not. That distinction changes Soul Urge and Personality, and it is fiddly enough that many implementations skip it and pick one answer for all cases. Chaldean sidesteps the issue: Y is always 1 and always a consonant for the vowel split.

So which should you use?

The honest answer is that this is a question about which tradition you are consulting, not which is correct — there is no external fact for either to be correct about. Chaldean is the older attribution and the one you will meet from an Indian practitioner. Pythagorean is the one nearly all English-language material assumes, so if you want your numbers to match the books you are likely to read, use it.

What we would argue for is not picking one but seeing both. Where the two tables agree about you, the reading rests on something more stable than a single author's letter assignments. Where they disagree, that disagreement is itself information: it tells you the finding is an artefact of the system rather than of your name.

What we do

Both tables are implemented, both are marked canonical, and every result on the site names the table and the source behind it. Three further systems — Kabbalah, Tamil and Hebrew — are implemented but marked contested, because we could not find a single citable source for any of them. Our reasoning for each is on the sources page.