How to Read a US Patent Number

US patent numbers look simple on the surface, but the format carries real information. Knowing how to interpret a patent number helps you find the right record, understand what type of patent you're looking at and avoid mistakes when searching.

The basic utility patent number

Most utility patents are identified by a plain number, sometimes written with the country code prefix "US" and formatted with commas for readability. For example:

• US 7,654,321
• US 10,234,567
• US 11,000,000

The USPTO has granted over 11 million utility patents. Older patents have shorter numbers; more recent ones have more digits. A patent number in the 4 millions was likely granted in the 1970s or 1980s. A number in the 10 millions is from the 2010s.

This rough correlation can be useful. If someone cites "US Patent 2,345,678" you know it's old technology, probably from the 1940s or 1950s and almost certainly expired.

Design patent numbers start with "D"

Design patents use a different numbering sequence with a "D" prefix. Examples:

• US D 789,000
• USD789000

Design patent numbers and utility patent numbers are counted separately, so "D 789,000" is different from "7,890,000."

Plant patent numbers start with "PP"

Plant patents use a "PP" prefix:

• US PP 27,500

Again, a separate number sequence from utility and design patents.

Reissue patents start with "RE"

If a patent is reissued after grant to correct errors, it gets a new number with the "RE" prefix:

• US RE 45,678

A reissued patent replaces the original and gets its own number, though its effective filing date is generally the same as the original.

Patent application publication numbers

Before a patent is granted, the application is published (typically 18 months after filing) with a publication number in a different format:

• US 2019/0123456 A1

The format is: country code, year of publication, a 7-digit sequential number and a document kind code. The "A1" indicates a first publication of an application. These are applications, not granted patents. The published application number is different from the eventual patent number if and when the patent grants.

How to search by patent number

The USPTO's Patent Center accepts patent numbers in several formats. You can enter:

• Just the number: 7654321
• With commas: 7,654,321
• With the D prefix for design: D789000
• With "US" country code: US7654321

The Patent Sunset calculator accepts standard utility, design and plant patent formats. When entering a number, you don't need the commas or country code prefix. Just the number or number with its type prefix works.

Common mistakes

Confusing application numbers with patent numbers. If someone gives you a number like "US 2019/0123456," that's a published application, not a granted patent. Published applications have a slash in the number. Granted patents don't.

Missing leading zeros. Some older patent numbers appear in sources with leading zeros dropped. US Patent 00056789 is the same as 56789.

Mixing up design and utility. If you're looking at a "D" number and treating it as a utility patent number, you'll find the wrong record or nothing at all.

Citing the wrong jurisdiction. US patent numbers don't include country prefixes in most databases. A European Patent Office number (EP 1234567) or a World Intellectual Property Organization publication number (WO 2019/123456) follows completely different formats.

What the number doesn't tell you

The patent number doesn't directly encode filing date, expiration date, technology class, or assignee. For any of those details, you need to look up the actual patent record.

For expiration date specifically, the number is just the key to find the patent. The expiration calculation requires the filing date, patent type, PTA data and maintenance fee status from the patent record, not from the number itself.