Pythagorean vs Chaldean numerology

The short answer

Pythagorean numerology gives the letters the values 1 to 9 in alphabetical order and reads the full birth name. Chaldean numerology gives the letters values from 1 to 8 by sound, never uses 9, and reads the name a person goes by now. The same name usually gets a different number in each system.

	Pythagorean	Chaldean
Traced back to	Pythagoras, ancient Greece	The Chaldeans of ancient Babylon
Letter values	1–9	1–8 (9 is never given to a letter)
How letters are valued	In alphabetical order	By the letter’s sound
Which name	The full name at birth	The name currently in use
Master numbers	11, 22 and 33	Usually 11 and 22
Two-digit totals	Reduced to one digit	Compound number kept as well, written like 37/1
Where it is used	Most English-language numerology	Older and more traditional practice
Numbers from the birthdate	Add up the digits of the date	Add up the digits of the date

The two letter charts

Pythagorean: the alphabet in rows of nine.

1	2	3	4	5	6	7	8	9
A	B	C	D	E	F	G	H	I
J	K	L	M	N	O	P	Q	R
S	T	U	V	W	X	Y	Z

Chaldean: eight groups, not in alphabetical order.

1	2	3	4	5	6	7	8
A I J Q Y	B K R	C G L S	D M T	E H N X	U V W	O Z	F P

Ten letters have the same value in both: A, B, C, D, E, J, K, L, M and N. The other sixteen change value, so most names add up differently.

One name through both systems

Take David James Miller.

	Pythagorean	Chaldean
David	4+1+4+9+4 = 22	4+1+6+1+4 = 16
James	1+1+4+5+1 = 12	1+1+4+5+3 = 14
Miller	4+9+3+3+5+9 = 33	4+1+3+3+5+2 = 18
Total	67 → 13 → 4	48 → 12 → 3 (read as 48/3)

The arithmetic is the same and neither result is a mistake. The two systems value the letters differently, so they produce different numbers. And if David has always gone by “Dave Miller”, a Chaldean reading would start from that name instead and could reach yet another number.

The numbers that come from the birthdate are a different story. Life path, personal year and similar numbers add up the digits of the date, so both systems agree on them.

Which system should you use?

• For a general, English-speaking audience, use Pythagorean. Most books, websites and calculators your users will check you against use it. If you show a Chaldean number, they will think your app is broken.
• For an audience that practises Chaldean numerology, use Chaldean, because a Pythagorean number will look wrong to them.
• Whichever you choose, say which one it is. Show the system next to every number, so a user who compares your result with another source can see why the two differ.

For more on where the systems came from and how they treat compound numbers, read Pythagorean vs Chaldean: what actually differs.

Pythagorean charts from an API

Simple Numerology API computes Pythagorean charts and states the system in every response:

curl -X POST https://simplenumerologyapi.com/v1/charts/pythagorean \
  -H 'X-API-Key: nk_…' \
  -H 'content-type: application/json' \
  -d '{"first_name":"David","middle_name":"James",
       "last_name":"Miller","birthdate":"1988-07-21"}'

{
  "object": "chart",
  "system": "pythagorean",
  "conventions": {"y_rule": "consonant", "name_reduction": "whole_name", "transliteration": "none"},
  "computed_name": "david james miller",
  "destiny": 4,
  "soul_urge": 3,
  "personality": 1,
  "…": "47 fields in all"
}

• The chart above, exactly as shown: full birth name, master numbers 11, 22 and 33 kept, and Y a consonant by default.
• The rules practitioners disagree on are options: Y as a vowel, reducing each name separately (the Decoz method) and transliteration of letters such as ø and ß. Every response echoes the rules it used in conventions.
• Results never change once published. Default output is pinned by a test, and any change ships as a new dated API version.

Frequently asked questions

What is the main difference between Pythagorean and Chaldean numerology?

The letter values. Pythagorean numbers the alphabet 1 to 9 in order, while Chaldean gives letters the values 1 to 8 by sound and never uses 9. The two also read different names: Pythagorean uses the full birth name, Chaldean the name in current use.

Which is more accurate, Pythagorean or Chaldean numerology?

Neither can be shown to be more accurate. They are two traditions with different rules. Pythagorean is the more widely used in English, while Chaldean is the older system.

Why is 9 not used in Chaldean numerology?

The Chaldean tradition treats 9 as sacred, so no letter is given that value. A name’s total can still reduce to 9.

Is the life path number the same in both systems?

Yes. The life path number comes from the birthdate, not from letters, so both systems add up the same digits and get the same result.

Does Simple Numerology API support Chaldean numerology?

No. It computes Pythagorean charts only, and every response says so in its system field. If your users expect Chaldean numbers, it is better to know before you integrate.

Can I calculate a Chaldean number myself?

Yes. Value each letter of the name with the Chaldean chart above, add the values, then add the digits of the total until one digit remains. Note the two-digit total as well, since Chaldean readings use it.