Why does NFC use 13.56 MHz and not another frequency?
NFC operates at 13.56 MHz because that frequency is a compromise. It is low enough that a tap happens deep inside the near field, where energy transfers by induction rather than radiating away. It is high enough that a coil of a few printed turns works, and that data rates of hundreds of kilobits per second are possible.
A frequency nobody has to license
13.56 MHz sits in a band set aside internationally for industrial, scientific and medical use. Equipment can transmit there without an individual licence, which is why the same tag works in Tokyo and in Lisbon and why a sticker can cost a few cents. Footnote 5.150 of the ITU Radio Regulations designates 13 553 to 13 567 kHz for industrial, scientific and medical applications, centred on 13 560 kHz. The NFC Forum builds its specifications on that band.
Contactless smart cards were already using it before NFC existed. Choosing it meant inheriting a decade of deployed readers rather than starting from nothing.
What 13.56 MHz means in metres
A radio wave at 13.56 MHz has a wavelength of about 22 metres. That number explains more about NFC than any other single figure.
The region close to an antenna where the magnetic component of the field dominates, and where energy can be transferred by induction rather than radiated away, extends roughly to the wavelength divided by two pi. At 13.56 MHz that is about 3.5 metres. A phone held against a tag is therefore not slightly inside the near field, it is a hundred times deeper than the boundary.
That is the whole trick. The reader is not broadcasting to the tag. The two coils are coupled, like the windings of a transformer separated by air.
Why not go lower
Low frequency RFID, around 125 kHz, is still in use for animal tags and older access badges. It penetrates water and tolerates metal far better than 13.56 MHz does, which is a genuine advantage.
The cost is bandwidth. A carrier at 125 kHz cannot carry hundreds of kilobits per second, so a low frequency tag transmits an identifier and little else. Antennas also grow: at a longer wavelength you need many more turns of wire to couple the same energy, which is why 125 kHz tags tend to be thick discs rather than paper thin labels.
Why not go higher
UHF RFID works around 900 MHz and reads from several metres. The wavelength there is roughly 33 centimetres, so at reading distance you are in the far field: the reader genuinely radiates, and the tag backscatters part of that radiation.
Far field coupling buys distance and loses everything else. Reading becomes possible without intent, which is precisely what you do not want for a payment card. The reader hardware is bigger and more expensive, and no phone carries it. GS1 publishes the standards that most UHF deployments follow.
Between the two, 13.56 MHz gives short deliberate range, an antenna that can be printed as a few flat turns on plastic film, and enough bandwidth to move a URL or run a payment exchange.
What this means when you buy a tag
Anything sold as an "NFC tag" works at 13.56 MHz. If a supplier offers a tag at 125 kHz or at 900 MHz, no phone will read it, whatever the listing says. That is the single most useful consequence of the frequency for a buyer.
It also explains why tags of the same frequency but different antenna sizes behave so differently. The frequency fixes the physics, the antenna fixes the coupling, and the coupling fixes the distance you actually get.
Frequently asked questions
Is 13.56 MHz the same frequency as contactless bank cards?
Yes. Contactless payment cards work at 13.56 MHz, which is why a phone can read parts of one. Reading a card and being able to charge it are entirely different things: the payment exchange requires cryptographic material a general purpose application never sees.
Can an NFC tag work at a different frequency?
Not and still be an NFC tag. The frequency is fixed by the specification. A 125 kHz or 900 MHz tag is an RFID tag, and no phone has hardware for those bands, so no application can read it.
Does the frequency explain why NFC fails on metal?
Partly. A conductive surface near the antenna distorts the magnetic field and shifts the tag away from the frequency it is tuned to. Lower frequencies tolerate this better, which is one reason some industrial systems still use 125 kHz.
Why is 13.56 MHz described as high frequency when Wi-Fi is much higher?
The label comes from the radio spectrum bands rather than from everyday comparison. The high frequency band runs from 3 to 30 MHz. Wi-Fi and Bluetooth sit in the ultra high frequency range and above, well past it.