What is the maximum read/write range of a low-cost passive HF RFID reader…

RFID (Radio-Frequency Identification) modules communicate with a tag through short-range electromagnetic coupling between the reader's antenna coil and the tag's own coil. In a passive design the tag draws all of its operating power from this induced field, so the distance over which reliable coupling, and hence reading, is possible is bounded by the reader's antenna size and transmit power. Manufacturers state this bound in the datasheet as the module's maximum read/write operating distance.

The standard low-cost passive HF (13.56 MHz) RFID reader module widely used in embedded-systems and IoT coursework is the MFRC522/RC522. Its datasheet specifies a typical maximum read/write operating distance of about 50 mm under normal conditions, and independent module references for the same board state a 5 cm read range. This 5 CM figure also matches the key recorded for the same question in the Bihar STET Computer Science official paper.

• A range of 10 CM would need a reader coil about that size — larger than the compact module's antenna loop, so it overstates the achievable coupling distance.

• A range of 15 CM would need a coil close to that size — well beyond what the compact module's loop antenna sustains, overstating the distance even further.

• A range of 2 CM would need a coil only about that size — smaller than the compact module's antenna coil, understating the distance the module actually achieves.

So the maximum read range of the module is 5 CM.