Phone and License Plate Numerology: The Last-Four-Digits Rule
In Taiwan, and in Japan and Korea too, you will hear that phone numbers and license plates can be lucky or unlucky. The most common rule takes the last four digits, divides them by 80 and looks up the remainder in the 81 numbers of Chinese name numerology. The calculator below does exactly that, and this page lays out where the methods disagree and what the numbers look like across all 10,000 possible endings.
Phone and plate number check
Enter a phone number or license plate. The tool keeps only the digits, applies the most common rule (last four digits divided by 80) and reads the remainder against two versions of the 81-number table, with the "sum of all digits" method shown for comparison. The number is calculated in your browser and is never sent or stored.
Readings compare two common versions of the table; where they disagree we say "Sources disagree". Glosses use neutral wording. We do not recommend changing a number because of its reading.
Last four digits ÷ 80, step by step
- Keep only the digits (letters on a plate, dashes and spaces are ignored).
- Take the last four, for example 5678 from 0912-345-678.
- Divide by 80 and keep the remainder: 5678 ÷ 80 = 70 remainder 78. Some write it as "divide by 80, drop the whole number, multiply by 80"; the result is the same.
- The remainder is the number to look up; a remainder of exactly 0 counts as 80 by convention.
| Example (fictional) | Digits used | Division | Number | Our reading |
|---|---|---|---|---|
| 0912-345-678 | 5678 | 5678 ÷ 80 remainder 78 | 78 | Mixed |
| ABC-2468 | 2468 | 2468 ÷ 80 remainder 68 | 68 | Auspicious |
| 0987-654-160 | 4160 | 4160 ÷ 80 remainder 0 | 80 | Sources disagree |
Why 80? The 81-number table is said to cycle, with 81 returning to 1 (numbers above 81 have 80 subtracted), so 80 is the divisor. Two consequences are rarely mentioned: with this rule 81 never comes up, because the remainder can only be 1 to 80; and because 10,000 is exactly 125 × 80, dividing the whole phone number by 80 gives the same remainder as dividing only the last four digits, so the earlier digits never matter.
All 10,000 endings: "unlucky" numbers are common
How we counted: of the 10,000 endings 0000–9999, each remainder from 1 to 80 occurs exactly 125 times (10,000 ÷ 80), so each share is the count of that kind of number among 1–80 times 1.25%. Readings follow the 81 numbers page.
In other words, roughly one number in 3 lands on a number both versions call inauspicious. Picking numbers by this rule would rule out a large part of the choice, and 9 of the numbers (29, 38, 55, 57, 58, 61, 72, 73, 80) are read in opposite ways by the two versions anyway.
Two methods, often two answers
Besides the last-four-digits rule, another method in circulation adds up every digit (subtracting 80 above 81) and looks that up. Different methods give the same phone number different readings:
| Example (fictional) | Last four ÷ 80 | Sum of digits |
|---|---|---|
| 0912-345-678 | 78 (Mixed) | 45 (Auspicious) |
| ABC-2468 | 68 (Auspicious) | 20 (Inauspicious) |
| 0987-654-160 | 80 (Sources disagree) | 46 (Inauspicious) |
There is no agreed standard. The calculator uses the last four digits as its main method and the digit sum for comparison, so you can see that the "luck" depends on which method you pick.
License plates
Taiwanese plates are usually letters plus four digits (for example ABC-2468), and the custom is to count only the digits, so the rule is the same as for a phone number. Japanese plates end in a number of up to four digits and Korean plates in four digits, and the same rule is applied to those. Some schools convert letters into numbers too, but every school converts differently, so we leave letters out. If a plate has fewer than four digits, all of them are used.
Where number readings come from, and their limits
The 81 numbers were made for counting the strokes of a name (see how the Five Grids work) and were popularized by Kumasaki Kenō in early 20th-century Japan. Applying them to phone numbers and plates is a later spin-off with no classical source and no single agreed method. What actually affects daily life is whether a number is easy to remember, easy to mistype, and how much trouble it is to tell everyone a new one.
Common misconceptions
Swap an unlucky number and your luck turns.
About 32.5% of all four-digit endings fall on a number both versions call inauspicious, and the tables disagree among themselves. We do not recommend changing a number over its reading.
Any number with a 4 in it is unlucky.
Avoiding 4 comes from its sound (it sounds like the word for death in Chinese, Japanese and Korean), which has nothing to do with the 81 numbers; by the last-four-digits rule a number containing 4 can easily read as auspicious.
Plates are only accurate if you count the letters.
Every school converts letters differently, and the most common practice counts digits only; change the conversion and the result changes with it.
Read on
A straight word: the Five Grids are a modern Japanese method, not an ancient one
The popular Five Grids method (Heaven, Person, Earth, Outer and Total grids read against the 81 numbers) was put together by the Japanese author Kumasaki Kenō in the early 20th century and later became common in Taiwan. It is not a classical Chinese tradition, and schools disagree both on how to count strokes and on which numbers are lucky. What makes a name good is its meaning, its sound, how it feels to write, and what it means to you; none of that is measured by strokes. We don't recommend changing a name because of an "unlucky" number. Everything on this site is for reference and entertainment.
Beyond numbers, read your BaZi chart
You can change a phone number, but not your birth time. Enter your birth date for a free Four Pillars chart with its Five Elements and Ten Gods.
Phone and plate number FAQ
How is a phone number read in Chinese numerology?
The most common rule takes the last four digits, divides by 80 and reads the remainder (0 counts as 80) against the 81-number table. Other methods, such as adding up all the digits, give different results.
How are license plates read?
By custom only the digits on the plate are used, usually four, with the same rule as a phone number: divide by 80, keep the remainder and look it up in the 81 numbers.
Should I change an unlucky number?
We don't recommend it. Of the 10,000 endings 0000–9999, about 32.5% fall on a number both versions call inauspicious, and the readings vary by source. A number that is easy to remember matters more.
Why does 81 never come up?
The remainder after dividing by 80 can only be 0 to 79, and 0 counts as 80, so this rule only ever gives 1 to 80.
How is this different from Eastern Numerology?
The 81-number method divides the last four digits by 80 and looks up the result. Eastern Numerology (the Number I Ching) instead pairs each two neighboring digits of the whole number and matches them to eight stars such as Sheng Qi and Tian Yi, looking at which stars appear and which dominates. The two methods are unrelated and their results do not convert.