RFID/NFC Read Range Calculator & Formula

For passive RFID and NFC, the tag has no battery. The core calculation is determining the maximum range at which the reader can transfer enough power to activate the tag’s chip. Purpose: To estimate the maximum theoretical read range of a passive RFID/NFC system.

Use this RFID/NFC Read Range Calculator to estimate the read range of your RFID or NFC system based on various input parameters. This tool helps engineers and developers optimize tag, antenna, and reader designs for better performance.

RFID & NFC Range Calculator Example:

Scenario: A UHF RFID reader portal.

** Inputs:**

• Frequency = 915 MHz
• P_reader = 1 Watts
• G_reader = 6 dBi
• G_tag = 2 dBi
• Eta = 0.7
• P_tag_min = 1.2e-5 Watts

OUTPUTS:

• R_max = 15.83 meters

RFID/NFC Read Range Formula

Where,

• Frequency (in MHz) = Operating frequency of the RFID/NFC system
• P_reader (in Watts) = Transmit power of the RFID reader
• G_reader (in dBi) = Gain of the RFID reader antenna
• G_tag (in dBi) = Gain of the RFID tag antenna
• Eta = Power transfer efficiency between the reader and tag
• P_tag_min (in Watts) = Minimum power required to activate the RFID tag chip
• R_max (in meters) = Maximum theoretical read range of the RFID/NFC system

References

• RFID Basics
• NFC Technology Overview
• ISO/IEC 14443 (NFC) and ISO/IEC 18000 (RFID) standards.
• Datasheets for RFID/NFC reader ICs and tag ICs (e.g., from NXP, Impinj) are the only source for the critical P_reader and P_tag_min values.