RFID Card Number Converter — Decimal, HEX & Swapped Endian

Single Converter: Select your input format (Decimal, HEX, HEX Swapped, or Decimal Swapped), enter the card number and click Convert. All four formats are shown instantly.
What is Swapped Endian? Many access control readers (HID, EM4100) store card numbers with byte order reversed. Decimal 4274176999 is FEC2C3E7 in HEX, but E7C3C2FE in swapped byte order. Your software may require one or the other.
Bulk Convert: Upload a CSV or Excel file with card numbers in any one column. Use Download Template to get a starter file. The tool fills in all missing formats for download.
Which format does my system use? Check your access control software documentation. Most Wiegand-based systems use Decimal. HID systems often display HEX Swapped.

Single Card Converter

Input Format

Card Number (Decimal)

Invalid input for selected format. Please check your value.

Bulk Converter — CSV / Excel Upload

File Format Requirements

RFID Decimal	RFID HEX	RFID HEX (Swapped Endian)	RFID Decimal (Swapped Endian)
4274176999	(auto-filled)	(auto-filled)	(auto-filled)

Your file needs at least one column: RFID Decimal, RFID HEX, RFID HEX (Swapped Endian) or RFID Decimal (Swapped Endian). Accepted: .csv or .xlsx

About RFID Card Number Formats

RFID access control cards store a unique number as a 32-bit (4-byte) value. The problem is that different manufacturers and software systems read and display those bytes in different orders, which means the same physical card can show as four completely different numbers depending on which system you are using. This is the swapped endian problem, and it causes significant confusion when enrolling cards, migrating between access control systems or troubleshooting why a card is not being recognised.

A decimal value like 4274176999 converts to FEC2C3E7 in hexadecimal. If you reverse the byte order (swap the endianness), you get E7C3C2FE in hex, which as a decimal number is 3888366334. All four of these numbers refer to the exact same physical card. HID ProxCard readers, EM4100 cards, Wiegand-protocol readers and various access control management platforms all have their own conventions for which format they display and which they accept for programming.

Conversion Example

Same card, four formats

RFID Decimal: 4274176999 RFID HEX: FEC2C3E7 HEX (Swapped Endian): E7C3C2FE Decimal (Swapped): 3888366334

How do I know which format my system uses?

Check your access control software documentation. Most Wiegand-based systems display Decimal. HID systems often display HEX Swapped. If you can read the number off the back of a card, compare it to all four formats to identify which one matches.

How does swapped endian work?

A 32-bit number has 4 bytes. In little-endian (swapped) format the bytes are stored in reverse order. FEC2C3E7 becomes E7C3C2FE when each pair of hex digits (each byte) is reversed in sequence: FE, C2, C3, E7 reversed becomes E7, C3, C2, FE.

Can I bulk convert a list of card numbers?

Yes. Download the Excel template, fill in your card numbers in any one of the four columns, upload the file and the tool fills in all missing formats. Download the result as Excel or CSV for import into your access control system.

Common Use Cases

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System migration. Moving from one access control system to another? Convert your existing card database to the format the new system expects without re-enrolling every card manually.

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Card enrolment troubleshooting. A card works at the reader but will not enrol in the software? The reader and software may be displaying different formats. Convert between them to find the matching number.

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Bulk card provisioning. Upload a spreadsheet of card numbers from procurement and get all four formats in a downloadable file ready to import into your access control database.

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Multi-site management. Different sites using different reader brands may report card numbers in different formats. Use this tool to normalise them to a single format for central management.