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
- Avoid using tags 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.
Which NFC tag size should you use ?
In short, use the largest tag you can but don’t go bigger than around 40mm.
Optimum antenna size
Put simply, for mobile phone use, Seritag 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 the quality of the manufacturing process and the skill of the manufacturer. 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 the cut of the sticker circle.
If they are good and they know what they are doing, 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 the size of the antenna as well as the size of the sticker. For all out stickers, we list the size of the antenna alongside the size of the label itself.
What is NFC scanstrength ?
ScanStrength was a term created by the Seritag team to make it easier to understand the comparative difference between tag performance.
As the actual scan distance will vary a lot between mobile phones and USB readers, a relative scale, which we called ScanStrength gives a good idea how one tag can be expected to perform next to the other.
Later in 2019, we are going to launch Real ScanStrength which will be an actual distance in mm for each tag. The Real ScanStrength will be an average of ten of the most popular mobile phones and USB readers.
ScanStrength (or scan strength) is important because it relates to how easy a tag is scan. It’s essentially how close the mobile phone needs to be to the tag before the tag will respond. A strong ScanStrength is important in any situation but understanding the differences will help understand which tag to choose.
For instances where the user is expected to be in close proximity – for example where they might be scanning the box of a product – then a low ScanStrength is usually adequate.
In instances where the user may be further away – such as a smart poster – then the very highest ScanStrength is important.
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.