By size, I mean how many GBs or TBs of data storage I would need to save entire blockchain starting from Genesis block when all bitcoins are mined?

  • I think you mean 2140, not 2040. – Nick ODell Mar 1 '15 at 19:39
  • Yes. I misread somewhere as 2040. Thanks for correction – balki Mar 1 '15 at 19:43
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    The best one could do in an answer is provide a range - because the size of the blockchain depends on the number of transactions, not the number of coins. If everybody immediately stopped trading bitcoins and only mined new ones, the blockchain would be much smaller than if every block was so full of transactions that it reached its maximum size. – Greg Hewgill Mar 1 '15 at 19:48
  • Size (GB / TB) has nothing to do with the 21 million limit or the year 2140. If you want to know the size of the blockchain in any arbitrary year the best you can do is simply extrapolate. But variables are usage (will bitcoin become popular?) and will the maximum (and average) block size grow? Increasing the maximum block size is being worked hard on by the core developers. – Jannes Mar 2 '15 at 13:20

The blockchain will not reach its maximum capacity by the year 2140, the only thing that is going to change is that all bitcoins (a little less than 21M bitcoins) will have been mined by then and the total number of blocks at that time will be around 6,929,999.

Assuming that a block's maximum size will remain 1 MB then we can estimate that the maximum blockchain size at that time will be ~6,6 terabytes.

Currently the average block size is 0,4 MB so if the usage remains in the same levels the estimated blockchain size will be around 2,64 terabytes.

A minimal block contains a single 1-input/1-output transaction. The tx size in this case is: 1 x 148 + 1 x 34 + 10 + 1 = 193 bytes. Adding 4 bytes for the magic number, 4 bytes for the blocksize indicator, 80 bytes for the block header and 1 byte for the transaction counter we come up with: 193 + 4 + 80 + 1 = 278 bytes or 0,0002651214599609375 MBs so if limits remain unchanged, the minimum blockchain size at that moment will be ~1,794 GB (~0,001752 TB).

For coinbase txs the tx size is ~233 bytes so the total size of the blockchain occupied by coinbase txs would be ~1,503 GB

So to sum up:

Min est. size: ~1,794 GB (~1,503 GB for coinbase-only txs)
Avg est. size: ~2,64 TB
Max est. size: ~6,6 TB

Note: The blockchain is currently ~36,5 GB so the above min value is only the theoretical limit, we already know that the blockchain size will be larger than today's ~36,5 GB.

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    This is a nice answer but your lower bound is not quite right. A minimal block can contain only the coinbase transaction, which can be smaller than 193 bytes (presumably because input signatures are not needed). Consider block 238440. It contains only a coinbase transaction, whose size is 152 bytes; the total size of the block is 233 bytes. – Nate Eldredge Mar 1 '15 at 20:18
  • @NateEldredge that is correct, I have updated my answer, thanks. – George Kimionis Mar 1 '15 at 20:33
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    Of course there are some people working very hard to increase the block limit beyond 1 MB, so the blockchain could be much bigger in that case. – Murch Mar 1 '15 at 21:51
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    @Murch true; the above calculations are based on the assumption: Assuming that a block's maximum size will remain 1 MB. And even then, this is just in theory. – George Kimionis Mar 1 '15 at 22:04

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