A full reading rests on six numbers. Two come from your date of birth, three from the letters of your full birth name, and one from combining the first two. Read on their own each describes a single facet; read together they describe how those facets pull with and against one another — which is the only thing a chart can do that a horoscope cannot.
The split matters more than it first appears. The date half of a chart is fixed and indisputable. The name half is neither: names change, and the tradition has never fully settled what to do about that. Numbers drawn from the two halves therefore carry different kinds of weight, and a reading that treats all six as equally solid is overstating five of them.
Life Path
Drawn from your date of birth. We reduce the month, the day and the year separately, then add the three results and reduce once more. It is usually taken as the through-line of a chart — the direction a life tends to return to, rather than a description of temperament.
It carries the most weight of the six for a plain reason: it is the only number nobody can argue you into changing. There is no spelling dispute, no question of which surname, no middle name anyone forgot. Calculate yours on the Life Path calculator, or work it out yourself in step 04 of the calculation guide.
Expression (Destiny)
Drawn from every letter of your full birth name. It describes the range of abilities you have to work with — what you are equipped to express, as distinct from what you want or where you are heading. The two names are used interchangeably for the same calculation; "Destiny" is the older label and rather overstates it.
Because it uses the whole name, Expression produces the largest totals in a chart, which makes it the number most likely to land on a master number or to pass through a karmic-debt total on the way down. See the Expression calculator.
Soul Urge (Heart's Desire)
Drawn from the vowels of your name. Read as inner motivation — what you are drawn toward when nothing is being asked of you, rather than what you are good at or how you come across.
It is built from very few letters, which has a practical consequence: Soul Urge is the number most sensitive to a single difference in spelling, and the one most affected by how a Y is treated. If your name contains one, calculate it both ways once and see how much moves. See the Soul Urge calculator.
Personality
Drawn from the consonants. Read as the impression you make before you are known — the part of you people meet first, and often the part they keep describing back to you.
It has one property worth knowing: the vowel total and the consonant total always add up to the Expression total, before any reduction. That makes Personality the arithmetic check on the other two, and the fastest way to find a dropped letter. See the Personality calculator.
Birthday
The day of the month you were born, reduced to a single digit. Read as one specific talent the chart leans on, rather than as a disposition — the narrowest claim of the six, and usefully so.
Its real job in a reading is corroboration. When it repeats the Life Path or the Soul Urge, that theme is doubled and can be leaned on harder; when it stands alone it stays a single talent. See the Birthday calculator.
Maturity
Your Life Path and Expression added together and reduced — the date half of the chart combined with the name half. Traditionally read as a theme that comes forward later in life, once the other numbers have been lived with rather than merely described.
Because it is derived from two numbers you have already read, it adds emphasis more often than information. Its most interesting property is the route: a Maturity number frequently passes through 13, 14, 16 or 19 on its way down, and that intermediate total is the part worth noticing.
What is not among the six
Plenty of numerology sits outside the core, and conflating it with the core is a common way to end up with an unreadable chart. Personal year, month and day are cycles — they describe a period, not a person, and they change. Pinnacles and challenges divide a life into four spans. Karmic lessons come from absence rather than addition: the digits no letter of your name carries. And angel numbers are not calculated from you at all.
Reading them together
No single number is a verdict. The interest is in the tension between them — a motivation (Soul Urge) that runs against the outward impression (Personality), or a direction (Life Path) the available abilities (Expression) do not obviously serve. A chart whose six numbers all agree is not a better chart; it is usually a less informative one.
To see all six at once, use the full chart. For a worked reading of an example chart, including what to do when two numbers openly conflict, see how to read your chart. For the arithmetic behind each, see our method — or the glossary if a term here is new.