How a life path number calculator works
Every life path calculator does the same three-line sum. This page shows the sum, so that you can verify any calculator’s output on paper — including the two places where honest calculators legitimately disagree with each other.
The procedure
Step one: write the date as a plain string of digits. Day, month, then all four digits of the year. 14 August 1984 becomes 1481984.
Step two: add every digit. 1 + 4 + 8 + 1 + 9 + 8 + 4 = 35.
Step three: if the total has more than one digit, add its digits. 3 + 5 = 8. Repeat until one digit is left.
Step four, the only conditional one: if at any point the total is 11, 22 or 33, most calculators stop there instead of reducing further.
That is the whole algorithm. A calculator that produces something else is either using the second convention below or is wrong.
A case with a master number, and a case without
29 January 1970: 2 + 9 + 1 + 1 + 9 + 7 + 0 = 29, then 2 + 9 = 11. A calculator that keeps master numbers reports 11; one that does not reports 1 + 1 = 2. Both will say they gave you the life path.
27 September 1990: 2 + 7 + 9 + 1 + 9 + 9 + 0 = 37, then 3 + 7 = 10, then 1 + 0 = 1. Two reductions, no master number, no ambiguity — every calculator should agree on this one.
If two sites disagree on a date like the first and agree on a date like the second, you have found the reason rather than a bug.
The second convention, and a date that exposes it
Some calculators reduce the day, the month and the year separately before adding them. For most dates this makes no difference, because both routes leave the same remainder.
1 February 1970 is one where it does. Whole date: 1 + 2 + 1 + 9 + 7 + 0 = 20, then 2 + 0 = 2. Separately: day 1; month 2; year 1 + 9 + 7 + 0 = 17, then 1 + 7 = 8. Adding those: 1 + 2 + 8 = 11, and 11 is kept. One route gives 2, the other 11.
Neither is a mistake in itself. A calculator that does not tell you which route it took is the problem, because it has withheld the one thing that would explain the difference.
Checking a calculator in thirty seconds
Give it a date whose answer you already worked out by hand — 14 August 1984 should give 8, and 27 September 1990 should give 1. If either comes back different, stop there.
Then give it 29 January 1970. An 11 means it keeps master numbers; a 2 means it reduces them. Neither is wrong, but now you know which readings you are getting.
Finally, look for the chain. A calculator that shows 35 and then 8 is one you can check; a calculator that shows only 8 is asking to be believed.
Checking your working
- Do I add the century digits of the year?
- Yes. 1984 contributes 1 + 9 + 8 + 4 = 22. Dropping the century — using 84 instead — is the single most common hand-calculation error.
- What if the total is 11 at the first step?
- Then the two conventions agree for once: a first-step total of 11 is a master number under both. The disagreements appear when 11 shows up only on one of the two routes.
- Does a leading zero in the day or month change the sum?
- No. Zero adds nothing, so 08 and 8 give the same total. Written dates often carry the zero; it makes no difference to the arithmetic.
- Why do some calculators write 11/2 instead of 11?
- To show both readings at once: the master number and what it would reduce to. It is a notation, not a third convention.