# What is the average size of a bitcoin transaction?

I'm curious, since the inception of bitcoin, what is the average size (in bytes) of a bitcoin transaction?

To be clear, the easiest way to find this is not to take the size of the block-chain and divide it by the total number of transactions. This is because there is a little overhead associated with block headers. Transactions need to be accounted for one at a time for this averaging operation.

Has anyone taken the time to analyze this information and, if so, what were the results? To be clear, I am interested in this answer as the data is stored in uncompressed-bytes. I'm not interested in any textual (i.e. JSON) variation which might be used for network communication.

• I wonder if there's much point in trying to be accurate. You could simply count them sure. Be 100% accurate. But what does that number tell you? I'm pretty sure the average size has changed over the years. Compressed addresses. Multi sig addresses. P2SH. OP_RETURN. More spam? Less spam? Any average you determine now will be different next year. Maybe you don't want one number but a graph of the the average per month? Per week? What's your purpose for this? Commented Oct 15, 2014 at 22:53
• I don't need to know it perfectly, but +98% accurate would be great.
– RLH
Commented Oct 16, 2014 at 0:41
• 98% sounds pretty random again. But total blockchain size / number transactions would probably get you there already. Especially if you correct that using a minus constant blockheader size. (Yeah I know it's not really constant) Commented Oct 16, 2014 at 8:06
• Obviously, the correct way to get this answer to to calculate the size of these transactions and divide by the number of transactions executed and processed thus far. My margin of error, however, is because I'd be willing to accept this metric, even if it was calculated 2 years ago. The immediate average is certainly different than what is was a year or two ago. However, that difference is within my personal margin of error, thus the 2%.
– RLH
Commented Oct 16, 2014 at 11:23
• I doubt that. I wouldn't be surprised if transactions are getting bigger. Because of growing use of mulitisig and op_return and more. How can you want something almost 100% accurate but then say you don't mind a difference because you estimate that diff to be max 2% ? I Commented Oct 16, 2014 at 12:38

Quote from Gavin Andresen:

the average Bitcoin transaction is about 250 bytes big

https://bitcointalk.org/index.php?topic=813324.0 (2nd post, last sentence)

• I'm going to give you the answer mark because if there is anyone who's side comments on the issue are mostly correct, it's Gavin's or a couple other BTC core-devs. If someone posts something a little more empirical, however, you might lose the check. Otherwise, this was what I was looking for. Thank you!
– RLH
Commented Oct 17, 2014 at 10:53

Just to give a few exact numbers, the current average transaction size (of all existing transactions until block height 498920) is 522.45 bytes.

If we take into account just the first 100000 blocks, then the average transaction size was indeed 238.51 bytes.

This is a plot of the average transaction size (aggregated monthly):

The peak on mid 2015 is produced by this 999657-bytes transaction.

These values can be computed using BlockSci.