How many contacts fit on one tag?
One, in practice, and that is also the right number. A contact card is several hundred bytes, so a mid range chip holds one comfortably and two awkwardly. What breaks first is not the memory, it is what phones do when handed more than one contact.
What one contact costs
A contact card is text, and its size follows how many fields you include. A name, a mobile number and an email is compact. Add a company, a job title, a landline, a postal address and a photograph reference and it grows quickly.
Several hundred bytes is the realistic range for a useful card, which puts it beyond the smallest chips and comfortably within mid range ones.
The photograph is the trap. A contact card with an embedded image is not a few hundred bytes, it is tens of thousands, and it fits on no tag.
What happens with several
You can write more than one contact record, and what the phone does with them is not something you can rely on.
Some devices act on the first and ignore the rest. Some offer a choice. Some show a result the person does not understand. The specification does not force one behaviour, so the deployment behaves differently in different pockets.
That inconsistency is worse than a capacity limit, because it is invisible during testing on one device and shows up in the field across many.
When you genuinely need more than one
A shared reception desk, a two person practice, a stand at a trade show representing several people.
These are real, and the tag is the wrong place to solve them. A single link to a page listing everyone gives the visitor a choice they can see, works identically on every phone, and stays correct when someone joins or leaves.
The arrangement that works
One tag, one link, one page. The page offers a contact file to download for whoever the visitor picks.
The visitor gets the same single tap. You get the ability to fix a wrong number without reprinting anything. And the tag stays small enough that the cheapest chip is adequate, which matters when you are equipping a team.
Where each person carries their own card, a chip that mirrors its identifier lets every card be written identically while still resolving to the right person. One write serves the whole batch.
Frequently asked questions
Can I put a photo in the contact?
Not on the tag. An embedded photograph is far larger than any tag capacity, so the picture belongs on the page the tag points to.
Is a vCard the right format?
It is the format phones understand for contacts, and writing it directly is only worth it when there is no network. Otherwise a link to a page offering the same file is more flexible.
How many fields should I include?
As few as make the card useful. Every field is more bytes, a longer tap, and one more thing to become wrong.
Can two people share one tag?
Physically yes, and the result depends on the phone. A link to a page listing both is predictable everywhere and costs nothing extra.