To calculate your personal month number, add your personal year number to the calendar month and reduce the total to one digit. Your personal year is your birth month plus birth day plus the current year, reduced the same way. Other methods start the month on your birthday or swap it into your birth date, so answers differ.
TL;DR
- Personal month = personal year + calendar month, reduced to one digit. For someone born 7 August, October 2026 is 7 + 1 = 8.
- January and October, February and November, March and December always share a personal month number, because 10, 11 and 12 reduce to 1, 2 and 3.
- Three published methods gave the same number on only 5.7% of person-days in 2026, and three different numbers on 37.6%.
- This method's 流月 is the calendar rule: its middle value matched personal year + month on all 48,312 cases I checked.
- That number is one of five positions in a month chart, which also holds six two-digit pair codes.
How do you calculate your personal month number?
Add your personal year number to the number of the month, then keep adding digits until one is left. Three terms do all the work here. The personal year number is the number numerology gives one calendar year for one person: birth month plus birth day plus the current year. The personal month number is that year number plus the calendar month. Reducing a number, also called taking its digital root, means adding its digits again and again until a single digit remains, so 25 becomes 2 + 5 = 7.
A worked example: someone born on 7 August, looking at 3 October 2026.
- Personal year for 2026: 7 + 8 + 2 + 0 + 2 + 6 = 25, then 2 + 5 = 7.
- October: month 10, which reduces to 1 + 0 = 1.
- Personal month for October 2026: 7 + 1 = 8.
- Personal day for 3 October 2026: 8 + 3 = 11, then 1 + 1 = 2.
The personal day number is the same step one level down: the personal month number plus the calendar day, reduced. On this rule nothing changes mid-month except the day, and the month number holds from the 1st to the last day.
Why do two calculators give different personal month numbers?
Because they run different rules, not because one of them added wrong. I found three in print, and each is consistent with itself. They differ on two questions: what goes into the sum, and on which day a new month begins.
- A. Calendar month
- Adds: your personal year (birth day, birth month and the current year) plus the calendar month.
- Changes: on the 1st of every month, and the personal year itself on 1 January.
- Birth year: not used.
- Sources: numerologist.com's personal month calculator (updated 20 July 2026): “The Personal Month is calculated by adding your Personal Year Number to the calendar month number, then reducing to a single digit”, and “The Personal Month aligns with the calendar month”. And Pauline Edward's calculations page: “The Personal Year begins in January and ends in December.” Edward keeps 11 and 22 unreduced in the month; numerologist.com reduces every month to 1 to 9.
- B. Month from your birthday
- Adds: the digits of your whole birth date, with the birth month replaced by the month that is running.
- Changes: on your birth day of the month. The page's own example, for someone born on the 20th: “2/20-3/19是他2月份流月” (20 February to 19 March is his February month).
- Birth year: used.
- Source: 樂覺製所 (number-talk.com), 21 August 2019: “流月的部分，以生日的日數為基準下去看” (for the month, go by the day of your birthday), worked as “1990/02/20=23/5”.
- C. Month swapped into your birth date
- Adds: the digits of your whole birth date, with the birth month replaced by the current calendar month.
- Changes: on the 1st of every month, with nothing extra on 1 January, because there is no personal year step.
- Birth year: used.
- Source: 楠晞的塔羅天空, 14 June 2019: “算流月就把你的月換成現在的月，算流日就把你的日換成現在的日。” (for the month, swap your month for the current one; for the day, swap your day for today's).
Now one person on one day. Born 7 August 1992, looking at 3 October 2026:
- A: personal year 7, plus October's 1, gives 8.
- B: the 3rd comes before the 7th, so September's month is still running: 1 + 9 + 9 + 2 + 9 + 7 = 37, then 3 + 7 = 10, then 1.
- C: October goes into the birth date: 1 + 9 + 9 + 2 + 1 + 0 + 7 = 29, then 2 + 9 = 11, then 2.
Three answers for one person on one day: 8, 1 and 2. Watch when they move. On 7 October B turns to 2 and matches C. On 1 November A moves to 9 and C to 3, while B stays at 2 until 7 November. Across the new year A goes from 1 on 31 December 2026 to 9 on 1 January 2027, because the personal year steps from 7 to 8 as well as the month, while C goes from 4 to 2, the month alone. The 樂覺製所 page does not say where the month starts for someone born on the 29th, 30th or 31st in a shorter month; in my count it starts on that month's last day.
How often do the three methods agree?
All three agree on 5.7% of person-days in 2026. I ran the three rules over every birth date from 1 January 1970 to 31 December 2005, 13,149 of them, against every day of 2026: 4,799,385 person-days. All three gave the same number on 5.7% of them, and three different numbers on 37.6%. Pair by pair, for 2026:
- A and B: the same on 11.1% of person-days. For a single birth date this ran from 0% to 100% of the year.
- A and C: the same on 11.1%. For each of the 13,149 birth dates they matched in every month of 2026 or in none: whether they agree depends on the birth month and birth year, not on the day you ask.
- B and C: the same on 51.6%. They share a formula and differ only on when the month starts, so they agree from your birth day of the month to the end of each calendar month.
What that means for any “your number this month” article is short: before reading the number, find out which rule produced it. For the person born 7 August 1992, an 8 under one rule was a 1 and a 2 under the other two, on the same day.
Which rule does 流月 use?
The calendar rule, method A: the calendar month and the calendar year. 流年 (liú nián) is this method's year chart, 流月 (liú yuè) its month chart and 流日 (liú rì) its day chart. The code folds the twelve months into nine month roots and pairs each with the year's own number; the day chart pairs each day root with that month's middle value.
I checked the middle value of the app's month chart against “personal year plus calendar month, reduced” for every birthday of the year, 29 February included, in every year from 2020 to 2030. That is 48,312 cases, and none differed. The day chart's middle value matched “personal month plus calendar day, reduced” on all 1,470,588 day cases, and the year chart's number matched the personal year on all 4,026 birthday-years. So in this method the year changes on 1 January, not on your birthday, as how to calculate your personal year explains for the 流年. How we check the arithmetic sets out the checking process behind figures like these.
Why do January and October share a number?
Because the month is reduced before it is added, and 10 reduces to 1, 11 to 2 and 12 to 3. With the same personal year in both, January and October give one person the same personal month, and so do February and November, and March and December. In my check that held in 12,078 of 12,078 cases.
So twelve months fall on nine month charts, and every person meets all nine numbers from 1 to 9 in a year, three of them twice: 4,026 of 4,026 birthday-years did. For 7 August in 2026 the months run 8, 9, 1, 2, 3, 4, 5, 6, 7, then 8, 9, 1 again for October, November and December. Across everyone, nine month roots against nine year roots give 81 possible month charts, and the code produces exactly 81.
The birth year never enters method A. Everyone born on 7 August has a personal month of 8 in October 2026, whether they were born in 1960 or 2001. Methods B and C do use the birth year, which is one quick way to tell which rule a calculator is running: change only the year of birth and see whether the answer moves.
What does the month chart hold beyond one digit?
In this method the personal month number is the middle of a five-position chart, not the whole of it. The positions:
- Top left: the month root (October gives 1).
- Top right: the year root, the personal year (7 in 2026).
- Middle: the two added and reduced, the personal month (8).
- Bottom left: the middle plus the top right: 8 + 7 = 15, then 6.
- Bottom right: the middle plus the top left: 8 + 1 = 9.
The chart is then read in pairs. Born 7 August, October 2026 gives 1, 7, 8, 6 and 9, and six two-digit pair codes, in the order the app lists them: 17, 18, 78, 86, 89 and 69. The day chart has the same shape with the day root top left and that month's middle top right. For 3 October 2026 it is 3, 8, 2, 1 and 5, with the codes 38, 32, 82, 21, 25 and 15.
Two of those day codes are master pairs. In this method a 5 sitting beside a 1, 2, 3, 6, 8 or 9 is also read as a doubled digit, so 25 is read as 22 and 15 as 11, and that holds on timing charts as well as birth charts, as why master numbers change every year shows. The same fold runs once more for the twelve hours of a day.
What this article does not tell you
What any of these numbers or pair codes means, in any of the three methods or in this one, and what this month holds for you. There is no forecast here. The meanings the quoted pages give belong to their publishers. The readings this method attaches to month and day charts are copyrighted practitioner material, so they are not on this site's public pages. What is here is the arithmetic, and all of it can be done by hand with a pen and a calendar.
Work out your root number and day master in the free calculator. It works them out in your browser and shows the arithmetic behind both, but it does not show a year, month or day chart. The year, month, day and hour charts are cast inside the account's Numerology module. That module is not part of the Free plan; it is switched on by request on WhatsApp.
FAQ
How do you calculate your personal month number?
Add your personal year number to the calendar month and reduce to one digit. The personal year is birth month plus birth day plus the current year, reduced. Born 7 August, in October 2026: 7 + 8 + 2 + 0 + 2 + 6 = 25, then 7; October gives 1; 7 + 1 = 8.
Does the personal month start on the 1st or on my birthday?
It depends on the rule. The calendar rule, which this method's 流月 uses, starts every month on the 1st. One published Chinese method starts it on your birth day of the month, so for someone born on the 20th, the February month runs from 20 February to 19 March.
Why do January and October have the same personal month number?
Because 10 reduces to 1 before it is added, just as 11 reduces to 2 and 12 to 3. With the same personal year, January and October come out equal, so do February and November, and March and December. One person's twelve months fall on nine month charts.
How do you calculate a personal day number?
Add the calendar day to your personal month number and reduce. For someone born 7 August, 3 October 2026 is 8 + 3 = 11, then 2. Substitution methods swap today's date into your birth date instead, which can give a different number.
Why do different calculators give different personal month numbers?
They run different rules: personal year plus calendar month, your birth date with this month swapped in, or that swap with the month starting on your birth day. Over every birth date from 1970 to 2005 and every day of 2026, all three agreed on 5.7% of days.
