US Passport Format Validator

US passport number: format, book vs card, and why there's no public checksum

A US passport number is the unique identifier printed on the data page, issued by the US Department of State. Modern passports use a 9-character number. For decades these were purely numeric (9 digits), but newer books use an alphanumeric format — typically a leading letter followed by 8 digits (e.g. C03005988). The number is unique to each document, not to the person: every renewal produces a new number.

Passport Book vs Passport Card

• Passport Book: the traditional booklet, valid for all international travel by air, land and sea. 9-character number.
• Passport Card: a wallet-sized card valid only for land/sea entry from Canada, Mexico, the Caribbean and Bermuda — not for air travel. Its number ends with the letter C in some encodings and has its own series.

No published check digit

The passport number itself has no publicly documented checksum. The check digits you see in the MRZ (the two machine-readable lines at the bottom of the data page) are computed by the ICAO 9303 weighting 7,3,1 over the passport number, birth date and expiry — but that's the MRZ's check, not a digit embedded in the number you'd type here. So format validation is limited to length and character class.

Common pitfalls

• Mistaking the MRZ check digit for part of the number: don't append the MRZ check digit to the passport number.
• Letter O vs zero / letter I vs one: alphanumeric passport numbers avoid ambiguous characters, but OCR errors are common — verify against the printed number.
• Format ≠ valid document: only the State Department can confirm a passport is genuine and unexpired.

FAQ

How many characters is a US passport number? Nine — older ones all digits, newer ones a letter plus eight digits.

Does it change when I renew? Yes. Each issued document gets a new number; the old number is retired.

Can I check it with a checksum? Not the number itself. Only the MRZ carries ICAO 9303 check digits, validated separately.