The life path number is the whole of numerology that most people ever meet. It is also the calculation most often done wrong, and the mistake is subtle enough that two sites can disagree about the same birthday without either noticing.
The method, and the mistake
Reduce the month to a single digit. Reduce the day. Reduce the year. Add those three results together and reduce once more. Stop at eleven, twenty two or thirty three at any stage rather than reducing them further.
The common shortcut is to write the date as one long string of digits and add them all at once. For most dates that gives the same answer. For some it does not, and the difference always involves a master number: reducing in one pass can pass straight through eleven or twenty two without stopping, which is precisely the distinction the system exists to make.
The calculator shows all three intermediate values and the total, so you can see the working rather than take a number on trust. If another site gives you something different, comparing the steps will usually show why within a few seconds.
What a master number is
Eleven, twenty two and thirty three are held back from reduction. In the tradition they are described as carrying the qualities of two, four and six at a higher pitch and with a correspondingly higher difficulty, which is the part that tends to be left out of the flattering versions.
Thirty three is rare enough that some practitioners do not use it at all, on the grounds that a number appearing so seldom cannot be studied properly. Whether you count it is a choice, and a calculator that silently reduces it to six has made the choice for you without saying so.
The personal year
The life path does not change, because the date it comes from does not change. What moves is the personal year: the same calculation with the current calendar year in place of your birth year. It runs on a nine year cycle and returns to one every ninth year.
When someone says their number has changed, this is almost always what they mean. The calculator lists the next few years so the cycle is visible rather than something you have to work out each January.
Where this sits
The arithmetic here is exact and entirely checkable. Add the digits yourself and you will get what the page got, every time. That is worth saying plainly, because it is the only part of numerology that can be verified.
What a number means is convention. It is a symbolic system, several centuries old in its modern form and drawing on much older ideas about number, and it makes no measurement of anything about you. This site keeps the arithmetic and the interpretation clearly apart, here as everywhere else, and does not tell you what your number says will happen.
Common questions
Why do life path calculators give different answers?
Almost always because one adds every digit of the date in a single sum while the other reduces month, day and year separately first. The separate method is the one that preserves a master number, and it is the method used here.
What is a master number?
Eleven, twenty two and thirty three are held back from reduction rather than being turned into two, four and six. A calculator that reduces them has discarded the one distinction the system treats as important.
What is a personal year?
The same calculation with the calendar year in place of your birth year. It moves on a nine year cycle and is the part of the system that changes, as opposed to the life path, which is fixed.
Is numerology astrology?
No. It is arithmetic on a calendar date and has nothing to do with the positions of anything. The two are often published side by side, which is why people assume a connection.
Can my life path number change?
No. It is derived from a date that does not change. The personal year changes annually, and that is what people usually mean when they say their number has moved.
What does the calculator not do?
It does not tell you what will happen, what work to take or who to be with. It gives you the number and the arithmetic behind it, and the meanings are marked clearly as convention.