Find out if your phone has NFC built in.
NFC tags (stickers and inlays) are available in a wide variety of sizes. The smallest stickers can be just 5-6mm square. The largest is typically about the size of a credit card at around 85mm x 55mm. How they perform is dependent on a number of factors - not least how well the tags are made.
Choosing which size is right for you will always come down to your particular application but as a general guideline consider the following points :
NFC Tag Size Considerations
- Use the largest tag you can use up to 38/40mm
- Always consider the antenna size not the tag size
- Don't go smaller than 22mm diameter or 12x19mm rectangle
Fundamentally, there's no point including tags in your application unless everyone can scan them. The better the scan performance, the better the results. Apart from a small extra in additional shipping weight cost, there's almost never any price difference between smaller tags and larger tags - don't go too small.
Optimum antenna size
Put simply, for mobile phone use, NFC.Today recommend a 29/30mm or 38/40mm tag (typically a 25mm or 35mm antenna) as the best option. The larger credit card sized antennas rarely perform better with mobile phones and they are often slightly more expensive - so don't bother. The reason for the reduced performance is that the larger tags can require a greater amount of energy to create the current to power the chip, therefore the phone has to be held closer. Mobile phones relatively speaking don't produce much 'NFC power' so the larger size doesn't usually help.
For higher powered devices such as USB readers, you will often find a slight increase in performance with a larger, credit card sized antenna but even this is dependent on the antenna size of the active device (USB reader/phone).
Antenna size vs. tag size
An NFC tag is an antenna and chip encased in or stuck to plastic. Due to manufacturing tolerances, the size of that plastic support disc will be larger than the size of the antenna - you will have a border. The size of that border is typically dependent on how good the manufacturer was. If they aren't very good and have poor machinery, then they will increase the tolerance (size of the border) to make sure the antenna is always inside. If they are good, then the machines place the antenna (or die cut) with more accuracy. This means a high quality tag is likely to have a larger antenna size for a given size of tag. This is important. There's usually no benefit using a 38mm sticker if the antenna is just 25mm. The key here is to know who big the antenna size is as well as the size of the sticker.
You can see from the graph below that difference in the relative scan strength of the different antenna sizes. Again, remember that this is the size of the antenna not of the overall tag itself. There is a substantial increase from the size of a Midas tag (12mm x 19mm sticker size, 10mm x 17mm antenna size) to a 29mm round sticker size (25mm antenna). In fact, you might expect to be able to scan the tag from twice the distance.
* Antenna size for these figures is assumed to be the area taken to the outer extreme of the antenna.
It's therefore worth noting that for a general mobile phone use case, the 38mm sticker size (35mm antenna) is likely to provide the maximum performance.