How much data, on average, does a credit card transaction use?
Not sure if this is the correct place to ask, but when a credit card is swiped at a POS terminal, how much data is passed for the entire transaction? Please include references if available.
edit: I'm really looking for the number of kB/MB.
Answer
Depends on what you mean - but as a really quick answer without any of the specifics: on average less than 1 kilobyte.
If you swipe a magnetic card, the magnetic reader will read either track 1 or track 2 from the card. Track 1 is 79 characters, where as track 2 is 40 characters. For a magnetic card, this is obviously the entire data read from the card. See Magnetic stripe card.
For a chip card, many messages (APDU) are exchanged between the payment terminal and the chip of the card. I don't remember off hand on how much data there is exactly, but it is in the order of hundreds of bytes, not kilobytes. These are specified in EMV specifications, again Wikipedia gives a proper introduction: EMV.
If you are talking about communication between the payment terminal (or POS) and a server for online authorization, this is again different. The communication amounts are roughly comparable to chip communication, again in the order of hundreds of bytes, not kilobytes. They use ISO 8583 format, but there are a lot of differences between countries so the standard is not exact.
Then again, if you are talking about the clearing batch material that gets sent at the end of each day, that is also an ISO 8583 message, but it is in ASCII format. There is one transaction per line and a single transaction is usually less than 200 characters.
And, if you are talking about communication between POS and the server, or all information stored, or something similar then that depends entirely on the POS software!