International · Hong Kong
HKID check digit validator.
Validate a Hong Kong identity card number and see the expected check digit. Enter it with or without the brackets.
How it works: An HKID is one or two letters, six digits and a check digit in brackets, for example A123456(3). Letters count as A=10 to Z=35, a one-letter prefix is padded with a space worth 36, the eight values are weighted 9 down to 2, and the check digit is 11 minus the sum mod 11 (0 for 11, A for 10).
Inputs
Test values (not real people’s numbers):
Result
Enter a number and press Check.
How the Hong Kong HKID check works
An HKID is one or two letters, six digits and a check digit in brackets, for example A123456(3). Letters count as A=10 to Z=35, a one-letter prefix is padded with a space worth 36, the eight values are weighted 9 down to 2, and the check digit is 11 minus the sum mod 11 (0 for 11, A for 10).
| Step | What happens |
|---|---|
| 1 | Turn letters into numbers: A=10, B=11, up to Z=35. A one-letter prefix gets a leading space valued 36 |
| 2 | Weight the eight values (prefix pair plus six digits) by 9, 8, 7, 6, 5, 4, 3, 2 and add them |
| 3 | Check digit = 11 minus (sum mod 11). A result of 11 is written 0 and a result of 10 is written A |
Worked example, A123456: space = 36 x 9 = 324, A = 10 x 8 = 80, then 1x7 + 2x6 + 3x5 + 4x4 + 5x3 + 6x2 = 77. The total is 481. 481 mod 11 = 8, and 11 - 8 = 3, so the number is A123456(3).
What this tool cannot tell you
The Immigration Department does not publish a public tool that confirms a card number was issued. The check digit is printed in brackets and is not part of the card number itself. A passing result means the number is well formed. It does not mean it was issued, is current, or belongs to anyone. Official sources to use instead: Hong Kong Immigration Department.
Where each rule comes from
Not every issuer publishes its check rules. This table says, for each rule used here, who documents it and how firmly.
| Rule | Source | Status |
|---|---|---|
| Format of one or two letters, six digits and a check digit that can be 0-9 or A | Wikipedia, Hong Kong identity card (citing the Immigration Department's Smart Identity Card page) | Documented by third parties, cross-checked |
| Modulus 11 weights 9 to 2, A=10, space=36, A for 10 | The Immigration Department does not publish the algorithm in the sources checked. It is described identically by hkid_ops (Rust), the Perl Algorithm::CheckDigits::M11_001 module and KnugiHK's multi-language reference. | Not published; reverse-engineered |
Frequently asked questions
How is the HKID check digit calculated?
Letters become numbers (A=10 to Z=35), a one-letter prefix is padded with a space worth 36, the eight values are weighted 9 to 2, and the check digit is 11 minus the sum mod 11, with 10 written as A and 11 as 0.
Can the HKID check digit be a letter?
Yes. When the calculation gives 10 the check digit is the letter A. All other check digits are 0 to 9.
Does a valid check digit mean the HKID is real?
No. It only shows the digits and check digit agree. Anyone can compute a matching digit for an invented number.
Is it safe to enter an HKID here?
The calculation runs in your browser and nothing is sent, stored or logged. Only enter numbers you are entitled to use.
Sources
- Hong Kong Immigration Department, Smart Identity Card (retrieved 15 October 2026)
- Wikipedia, Hong Kong identity card (retrieved 15 October 2026)
- hkid_ops (Rust crate documentation) (retrieved 15 October 2026)
- KnugiHK, Hong Kong ID Card Verification Algorithm (retrieved 15 October 2026)
Format check only — not an official verification
This tool checks structure and, where a public algorithm exists, a check digit, entirely in your browser. It does not query any government register, and it cannot confirm that a number was issued or to whom. Nothing you type is transmitted, stored or logged.