How to check a Singapore car plate number
The last character of a Singapore registration number is a checksum, completely determined by the prefix and digits in front of it. Type the plate into the verifier and it is checked as you type — this guide walks the arithmetic once, so you can trust the verdict and know exactly what it cannot say.
How to run the check
- Enter the plate as printed, for example
SBA1234G. Spaces, hyphens and underscores are stripped and lower case is accepted, sosba 1234 gparses to the same plate. - The plate is split into its parts. A prefix of one to three letters, one to four digits, and an optional final letter. Anything outside that shape is rejected as malformed before any arithmetic happens.
- The six contributing characters are weighted and reduced modulo 19. The remainder selects the expected letter from a fixed nineteen-letter alphabet.
- Read the verdict. A valid result confirms the final letter matches what the formula demands and, if you left it off, tells you which letter to expect. A mismatch names the letter the plate should have carried.
Worked example: SBA1234G
The three-letter prefix sheds its first letter, so only B and A count. Letter values are one-based positions in the alphabet, A is 1 through Z is 26, and the digits pad left to exactly four:
| Slot | Character | Value | Weight | Product |
|---|---|---|---|---|
| L1 | B, the 2nd letter | 2 | × 9 | 18 |
| L2 | A, the 3rd letter | 1 | × 4 | 4 |
| D1 | 1 | 1 | × 5 | 5 |
| D2 | 2 | 2 | × 4 | 8 |
| D3 | 3 | 3 | × 3 | 9 |
| D4 | 4 | 4 | × 2 | 8 |
Sum is 18 + 4 + 5 + 8 + 9 + 8 = 52, and 52 mod 19 = 14, so the plate must end in the letter remainder 14 maps to, which is G. Change one digit — SBA1235G — and the sum becomes 54, 54 mod 19 = 16, which demands D instead.
Treat a pass as "this number is not a typo", never as "this vehicle exists". Cloning a plate is a physical act and the checksum is arithmetic, so a copied plate carries a copied checksum. Use this page to clean up transcribed data — dashcam stills, gate logs, handwritten notes, CSV exports — and use an official source for anything touching ownership or enforcement.
When a character is unreadable
The reverse solver takes a pattern with ? or * for characters you cannot make out and returns every registration that satisfies the equation. A gap at the checksum position always resolves to exactly one answer, because that letter was never a free choice. A gap in the digits is often unique; a gap in the second or third prefix letter can return many candidates, and the first 150 are listed on screen.
Limits worth knowing
- Lookalike characters are reported, not guessed. O and 0, I and 1, S and 5 are different characters, so an eye-read plate can fail two plausible ways — check both readings.
- The series label is a hint, not a record. It comes from a lookup table of known prefixes and falls back to a generic answer for series it does not recognise.
- Seven letters can never be a checksum. F, I, N, O, Q, V and W are left out of the alphabet, so a plate ending in one of them is malformed rather than unusual.
- Bulk pastes need the plate column only. Every other CSV column reads as its own row and counts as malformed, so paste one plate per line or separated by commas or semicolons.
Frequently asked questions
How do I check a Singapore car plate number?
Type the plate into the verifier, for example SBA1234G, and it is checked as you type. Spaces, hyphens and lowercase are accepted.
A matching final letter means the registration is well formed; a mismatch names the letter the plate should have carried, with the full calculation shown.
How is the checksum letter actually computed?
The prefix is reduced to two letter values, the digits are left-padded to four, and all six are weighted and added: L1 times 9, L2 times 4, then the digits times 5, 4, 3 and 2. The total modulo 19 selects the letter from a fixed nineteen-letter alphabet.
For SBA1234G the sum is 52, 52 mod 19 is 14, and remainder 14 maps to G.
Can I find a missing character on a plate I cannot read?
Yes. The reverse solver takes ? or * for characters you cannot make out and returns every registration satisfying the equation.
A missing checksum letter always resolves to exactly one answer. A gap in the digits is usually unique too, while a gap in the second or third prefix letter can return many candidates.
Does a valid checksum prove the vehicle is registered?
No. The checksum is a claim about the shape of the number, not about the world: no register is queried and nothing leaves the browser.
A physical copy of a valid plate is still valid arithmetic. Use the check to clean up transcribed data, and an official source for anything about ownership or enforcement.
How do I audit a whole list of plates at once?
Paste the plates one per line, or separated by commas or semicolons, into the bulk auditor. You get a total, a valid count, an invalid count, a pass rate, and a table with the letter each plate should have carried.
Export the passes as text or the full audit as CSV.